{"id":1027,"date":"2021-03-14T16:36:21","date_gmt":"2021-03-14T16:36:21","guid":{"rendered":"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/?p=1027"},"modified":"2021-03-15T14:10:27","modified_gmt":"2021-03-15T14:10:27","slug":"back-to-basics-a-new-way-of-solving-quadratics","status":"publish","type":"post","link":"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/2021\/03\/14\/back-to-basics-a-new-way-of-solving-quadratics\/","title":{"rendered":"Back to basics: A &#8216;New&#8217; Way of Solving Quadratics"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"1027\" class=\"elementor elementor-1027\">\n\t\t\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-d464b2f elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"d464b2f\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-44f88ab\" data-id=\"44f88ab\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-738c21c elementor-widget elementor-widget-text-editor\" data-id=\"738c21c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>Happy&nbsp;<span>\u03c0-day! To celebrate, l<\/span>et&#8217;s go all the way back to GCSE maths where we just little baby kids, most likely annoying (at least I was), learning about quadratic equations. Say we want to solve the following quadratic: <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> x^2\u00a0 &#8211;\u00a0 8x + 12 = 0<\/span> Solving this just means we want to find the values of x which makes the entire equation equal to 0. These values are called the <b>roots<\/b> of the equation. So how do we find the roots of the equation? One method is factorising.<\/p>\n<p>To factorise the above quadratic we want to find two numbers, let&#8217;s call them <i>r<\/i> and <i>s <\/i>such that we can rewrite the quadratic as <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> x^2\u00a0 &#8211;\u00a0 8x + 12 = (x\u00a0 &#8211;\u00a0 r) (x\u00a0 &#8211;\u00a0 s) <\/span> and <i>r <\/i>and <i>s <\/i>satisfy the following properties: <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r + s = 8 \\\\ rs = 12 <\/span><\/p>\n<p>The first property is the sum of r and s equal to 8 not -8 because of the negative signs in the brackets. If we can write our quadratic in this form, as two brackets, then the roots of the equation are <i>r<\/i> and <i>s<\/i>. How do we find <i>r<\/i> and <i>s<\/i>? Well this is where we&#8217;re taught to guess (and when I&#8217;ve taught this to students, I told them to guess too, woops). The second property says we multiply <i>r<\/i> and <i>s<\/i> to get 12, so that must mean r and s are factors of 12. So we search through all the factors of 12 and find a pair that add together to get 8. Luckily 12 doesn&#8217;t have lots of factors so we can see (relatively quickly) that our roots are <i>r<\/i> = 2 and <i>s<\/i> = 6. But having to guess isn&#8217;t very mathematical, and this method doesn&#8217;t work when the roots are quite ugly (involving irrational and\/or even imaginary numbers).<\/p>\n<p><b>So let&#8217;s look at this problem differently<\/b>. Pretend that I didn&#8217;t just tell you the answer and we still don&#8217;t know what <em>r<\/em> and <em>s<\/em> are. Instead of starting with the second property, let&#8217;s start with the first. We want two numbers that add together to get 8. Well, if two numbers <i>r<\/i> and <i>s <\/i>sum together to get 6, then the average (or mean) of these two numbers will equal 8\u00f72 = Happy4. If <em>r<\/em> and <em>s<\/em> have an average of 4, then that means&nbsp;<em>r&nbsp;<\/em>and&nbsp;<em>s <\/em>are equally distanced and on either side of 4.&nbsp;<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-09c0a15 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"09c0a15\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-cf587e6\" data-id=\"cf587e6\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-3a2f07f elementor-widget elementor-widget-text-editor\" data-id=\"3a2f07f\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>This means that we can write\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>as <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r = 4\u00a0 &#8211;\u00a0 d \\\\ s = 4 + d <\/span> where <em>d\u00a0<\/em>is some number representing the distance\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>are from 4. Now, this is actually great, we have some indication of what\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>are now! If we can just find out what the number\u00a0<em>d\u00a0<\/em>is, then we can just find out what\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>is directly!<\/p><p><span style=\"font-weight: bold\">So how do we find\u00a0<em>d?\u00a0<\/em><\/span>Well, let&#8217;s now use the second property but replace\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>with the equations involving\u00a0<em>d<\/em>. So we get <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> (4\u00a0 &#8211;\u00a0 d) (4 + d) = 12 <\/span> If we just expand this, we get <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> 16\u00a0 &#8211;\u00a0 d^2 = 12 <\/span> Okay, we&#8217;re getting somewhere. So rearranging this, we get <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> d = \\sqrt{16 &#8211; 12} = \\sqrt{4} = 2 <\/span> Now we know what <em>d\u00a0<\/em>is, we can put this back into our equations for\u00a0<em>r\u00a0<\/em>and\u00a0s. This gives us <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r = 4\u00a0 &#8211;\u00a0 2 = 2 \\\\ s = 4 + 2 = 6 <\/span><\/p><p>And we&#8217;re done, yay! But why go through all this fuss when we already have a method for solving quadratics? One reason is because the method before requires us to do a bit of trial and error in order to find the answer and it doesn&#8217;t always work on all quadratics. Whereas this method here is more systematic, requires no guess work, and works with all quadratics! But more importantly, this new method gives us a new perspective into what solving quadratics means.<\/p><p>Let&#8217;s look at the plot of the above quadratic.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-5d982a1 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"5d982a1\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-c3c3cdc\" data-id=\"c3c3cdc\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-72f2c29 elementor-widget elementor-widget-image\" data-id=\"72f2c29\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" width=\"663\" height=\"743\" src=\"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/wp-content\/uploads\/sites\/21\/2021\/03\/quadratic.png\" class=\"attachment-large size-large wp-image-1170\" alt=\"\" srcset=\"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/wp-content\/uploads\/sites\/21\/2021\/03\/quadratic.png 663w, https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/wp-content\/uploads\/sites\/21\/2021\/03\/quadratic-268x300.png 268w\" sizes=\"(max-width: 663px) 100vw, 663px\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Plot of the quadratic <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> y = x^2  -  8x + 12 <\/span> The roots and the turning point of the equation are marked with blue crosses. Lines are added to show that the roots are symmetrical around the turning point.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-c82f2ae elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"c82f2ae\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-7421846\" data-id=\"7421846\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-c26818f elementor-widget elementor-widget-text-editor\" data-id=\"c26818f\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>From the plot, we can see that the graph has a value of\u00a0<em>y = 0\u00a0<\/em>\u00a0exactly when\u00a0<em>x = 2\u00a0<\/em>or\u00a0<em>x = 6<\/em>, the roots of our equation. But moreover, these roots lie exactly on either side of the point\u00a0<em>x = 4<\/em>. Well, when\u00a0<em>x = 4<\/em>, the graph is at it&#8217;s lowest point. This point is what we call a\u00a0<span style=\"font-weight: bold\">turning point\u00a0<\/span>and for quadratics, everything is symmetric about the turning point. But we already knew that, because our quadratic equals to 0 exactly when our solutions took the form of 4<em>\u00a0\u00b1 2<\/em>, when our solutions are symmetric about 4.<\/p><p>The step-by-step method for solving generic quadratics is below.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-5b1379c elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"5b1379c\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-00df14a\" data-id=\"00df14a\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-38412ec elementor-widget elementor-widget-toggle\" data-id=\"38412ec\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"toggle.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-toggle\">\n\t\t\t\t\t\t\t<div class=\"elementor-toggle-item\">\n\t\t\t\t\t<div id=\"elementor-tab-title-5891\" class=\"elementor-tab-title\" data-tab=\"1\" role=\"button\" aria-controls=\"elementor-tab-content-5891\" aria-expanded=\"false\">\n\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon elementor-toggle-icon-left\" aria-hidden=\"true\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon-closed\"><i class=\"fas fa-caret-right\"><\/i><\/span>\n\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon-opened\"><i class=\"elementor-toggle-icon-opened fas fa-caret-up\"><\/i><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"elementor-toggle-title\" tabindex=\"0\">Method to solving quadratics<\/a>\n\t\t\t\t\t<\/div>\n\n\t\t\t\t\t<div id=\"elementor-tab-content-5891\" class=\"elementor-tab-content elementor-clearfix\" data-tab=\"1\" role=\"region\" aria-labelledby=\"elementor-tab-title-5891\"><p>We want to solve the following quadratic <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> x^2\u00a0 &#8211;\u00a0 bx + c = 0 <\/span> To do this, we wish to rewrite this quadratic as <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> x^2\u00a0 &#8211;\u00a0 bx + c = (x\u00a0 &#8211;\u00a0 r)(x\u00a0 &#8211;\u00a0 s) = 0 <\/span> where\u00a0<em>r\u00a0<\/em>and\u00a0<em>s <\/em>are the roots of the equation.\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>will take the form <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r = \\frac{b}{2}\u00a0 &#8211;\u00a0 d \\text{ , } s = \\frac{b}{2} + d <\/span> for some number\u00a0<em>d<\/em>. Find\u00a0<em>d\u00a0<\/em>by using <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> d = \\sqrt{\\frac{b^2}{4} &#8211; c} <\/span> Putting this value of <em>d\u00a0<\/em>back into the above equations for\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>gives us the roots of the quadratic equation, and therefore we will have solved the quadratic equation.<\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-aa2a92d elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"aa2a92d\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-d380ea0\" data-id=\"d380ea0\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-2245b2b elementor-widget elementor-widget-heading\" data-id=\"2245b2b\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-large\">Exercises<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-f435eaf elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"f435eaf\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-e5170fc\" data-id=\"e5170fc\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-d2fe678 elementor-widget elementor-widget-text-editor\" data-id=\"d2fe678\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>See if you can apply this method on the following quadratics, showing that our method works with whatever quadratic equation given.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-6057288 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"6057288\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-95741d1\" data-id=\"95741d1\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-6e9dbf3 elementor-widget elementor-widget-toggle\" data-id=\"6e9dbf3\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"toggle.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-toggle\">\n\t\t\t\t\t\t\t<div class=\"elementor-toggle-item\">\n\t\t\t\t\t<div id=\"elementor-tab-title-1151\" class=\"elementor-tab-title\" data-tab=\"1\" role=\"button\" aria-controls=\"elementor-tab-content-1151\" aria-expanded=\"false\">\n\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon elementor-toggle-icon-left\" aria-hidden=\"true\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon-closed\"><i class=\"fas fa-caret-right\"><\/i><\/span>\n\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon-opened\"><i class=\"elementor-toggle-icon-opened fas fa-caret-up\"><\/i><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"elementor-toggle-title\" tabindex=\"0\"><span class=\"wp-katex-eq katex-display\" data-display=\"true\"> x^2  -  10x + 24 = 0 <\/span><\/a>\n\t\t\t\t\t<\/div>\n\n\t\t\t\t\t<div id=\"elementor-tab-content-1151\" class=\"elementor-tab-content elementor-clearfix\" data-tab=\"1\" role=\"region\" aria-labelledby=\"elementor-tab-title-1151\"><p>So we want to find roots\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>such that <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> x^2\u00a0 &#8211;\u00a0 10x + 24 = (x\u00a0 &#8211;\u00a0 r) (x\u00a0 &#8211;\u00a0 s) <\/span> Expanding this, we can find\u00a0<em>r\u00a0<\/em>and\u00a0<em>s<\/em> by using the two equations <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r + s = 10 \\\\ rs = 24 <\/span> Using the first equation, the average of\u00a0<em>r\u00a0<\/em>and\u00a0<em>s <\/em>must be equal to 10\u00f72 = 5. Therefore we have <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r = 5\u00a0 &#8211;\u00a0 d \\text{ , } s = 5 + d <\/span> for some number <i>d.<\/i> Putting these equations of\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>into the 2nd property above, we get <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> (5\u00a0 &#8211;\u00a0 d) (5 + d) = 24 \\\\ 25\u00a0 &#8211;\u00a0 d^2 = 24 \\\\ d = \\sqrt{25-24} = \\sqrt{1} = 1<\/span> So now we&#8217;ve found\u00a0<em>d<\/em>. Substituting this value of\u00a0<em>d\u00a0<\/em>into the equations for\u00a0<em>r\u00a0<\/em>and\u00a0<em>s<\/em>, we find that our roots are\u00a0<span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r = 5\u00a0 &#8211;\u00a0 1 = 4 \\\\ \\text{ and } s = 5 + 1 = 6<\/span><\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<div class=\"elementor-toggle-item\">\n\t\t\t\t\t<div id=\"elementor-tab-title-1152\" class=\"elementor-tab-title\" data-tab=\"2\" role=\"button\" aria-controls=\"elementor-tab-content-1152\" aria-expanded=\"false\">\n\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon elementor-toggle-icon-left\" aria-hidden=\"true\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon-closed\"><i class=\"fas fa-caret-right\"><\/i><\/span>\n\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon-opened\"><i class=\"elementor-toggle-icon-opened fas fa-caret-up\"><\/i><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"elementor-toggle-title\" tabindex=\"0\"><span class=\"wp-katex-eq katex-display\" data-display=\"true\"> x^2 + 7x + 12 = 0 <\/span><\/a>\n\t\t\t\t\t<\/div>\n\n\t\t\t\t\t<div id=\"elementor-tab-content-1152\" class=\"elementor-tab-content elementor-clearfix\" data-tab=\"2\" role=\"region\" aria-labelledby=\"elementor-tab-title-1152\"><p>So we want to find roots\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>such that <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> x^2 + 7x + 12 = (x\u00a0 &#8211;\u00a0 r) (x\u00a0 &#8211;\u00a0 s) <\/span> Expanding this, we can find <em>r\u00a0<\/em>and\u00a0<em>s<\/em> by using the two equations <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r + s =\u00a0 &#8211;\u00a0 7 \\\\ rs = 12 <\/span> Using the first equation, the average of <em>r\u00a0<\/em>and\u00a0<em>s <\/em>must be equal to -7\u00f72 = -3.5. Therefore we have <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r = -3.5\u00a0 &#8211;\u00a0 d \\text{ , } s = -3.5 + d <\/span> for some number <i>d.<\/i> Putting these equations of\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>into the 2nd property above, we get <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> (-3.5\u00a0 &#8211;\u00a0 d) (-3.5 + d) = 12 \\\\ \\frac{49}{4}\u00a0 &#8211;\u00a0 d^2 = 12 \\\\ d = \\sqrt{\\frac{49}{4}\u00a0 &#8211;\u00a0 12} = \\sqrt{\\frac{1}{4}} = 0.5 <\/span> So now we&#8217;ve found <em>d<\/em>. Substituting this value of\u00a0<em>d\u00a0<\/em>into the equations for\u00a0<em>r\u00a0<\/em>and\u00a0<em>s<\/em>, we find that our roots are <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r = -3.5\u00a0 &#8211;\u00a0 0.5 =\u00a0 -4 \\\\ \\text{ and } s = -3.5 + 0.5 =\u00a0 -3<\/span><\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<div class=\"elementor-toggle-item\">\n\t\t\t\t\t<div id=\"elementor-tab-title-1153\" class=\"elementor-tab-title\" data-tab=\"3\" role=\"button\" aria-controls=\"elementor-tab-content-1153\" aria-expanded=\"false\">\n\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon elementor-toggle-icon-left\" aria-hidden=\"true\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon-closed\"><i class=\"fas fa-caret-right\"><\/i><\/span>\n\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon-opened\"><i class=\"elementor-toggle-icon-opened fas fa-caret-up\"><\/i><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"elementor-toggle-title\" tabindex=\"0\"><span class=\"wp-katex-eq katex-display\" data-display=\"true\"> x^2  -  8x + 13 = 0 <\/span><\/a>\n\t\t\t\t\t<\/div>\n\n\t\t\t\t\t<div id=\"elementor-tab-content-1153\" class=\"elementor-tab-content elementor-clearfix\" data-tab=\"3\" role=\"region\" aria-labelledby=\"elementor-tab-title-1153\"><p>So we want to find roots\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>such that <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> x^2\u00a0 &#8211;\u00a0 8x + 13 = (x\u00a0 &#8211;\u00a0 r) (x\u00a0 &#8211;\u00a0 s) <\/span> Expanding this, we can find <em>r\u00a0<\/em>and\u00a0<em>s<\/em> by using the two equations <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r + s =\u00a0 8 \\\\ rs = 13 <\/span> Using the first equation, the average of <em>r\u00a0<\/em>and\u00a0<em>s <\/em>must be equal to 8\u00f72 = 4. Therefore we have <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r = 4 &#8211;\u00a0 d \\text{ , } s = 4 + d <\/span> for some number <i>d.<\/i> Putting these equations of\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>into the 2nd property above, we get <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> (4\u00a0 &#8211;\u00a0 d) (4 + d) = 13 \\\\ 16\u00a0 &#8211;\u00a0 d^2 = 13 \\\\ d = \\sqrt{16\u00a0 &#8211;\u00a0 13} = \\sqrt{3}<\/span> We can leave <em>d <\/em>in this form, perfectly okay!\u00a0Substituting this value of\u00a0<em>d\u00a0<\/em>into the equations for\u00a0<em>r\u00a0<\/em>and\u00a0<em>s<\/em>, we find that our roots are <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r = 4\u00a0 &#8211;\u00a0 \\sqrt{3} \\\\ \\text{ and } s = 4 + \\sqrt{3} <\/span><\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<div class=\"elementor-toggle-item\">\n\t\t\t\t\t<div id=\"elementor-tab-title-1154\" class=\"elementor-tab-title\" data-tab=\"4\" role=\"button\" aria-controls=\"elementor-tab-content-1154\" aria-expanded=\"false\">\n\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon elementor-toggle-icon-left\" aria-hidden=\"true\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon-closed\"><i class=\"fas fa-caret-right\"><\/i><\/span>\n\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon-opened\"><i class=\"elementor-toggle-icon-opened fas fa-caret-up\"><\/i><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"elementor-toggle-title\" tabindex=\"0\"><span class=\"wp-katex-eq katex-display\" data-display=\"true\"> x^2  -  8x + 18 = 0 <\/span><\/a>\n\t\t\t\t\t<\/div>\n\n\t\t\t\t\t<div id=\"elementor-tab-content-1154\" class=\"elementor-tab-content elementor-clearfix\" data-tab=\"4\" role=\"region\" aria-labelledby=\"elementor-tab-title-1154\"><p>So we want to find roots\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>such that <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> x^2\u00a0 &#8211;\u00a0 8x + 18 = (x\u00a0 &#8211;\u00a0 r) (x\u00a0 &#8211;\u00a0 s) <\/span> Expanding this, we can find <em>r\u00a0<\/em>and\u00a0<em>s<\/em> by using the two equations <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r + s =\u00a0 8 \\\\ rs = 18 <\/span> Using the first equation, the average of <em>r\u00a0<\/em>and\u00a0<em>s <\/em>must be equal to 8\u00f72 = 4. Therefore we have <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r = 4\u00a0 &#8211;\u00a0 d \\text{ , } s = 4 + d <\/span> for some number <i>d.<\/i> Putting these equations of\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>into the 2nd property above, we get <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> (4\u00a0 &#8211;\u00a0 d) (4 + d) = 18 \\\\ 16\u00a0 &#8211;\u00a0 d^2 = 18 \\\\ d = \\sqrt{16\u00a0 &#8211;\u00a0 18} = \\sqrt{-2} = i\\sqrt{2} <\/span> So now we&#8217;ve found <em>d<\/em>. Substituting this value of\u00a0<em>d\u00a0<\/em>into the equations for\u00a0<em>r\u00a0<\/em>and\u00a0<em>s<\/em>, we find that our roots are <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r = 4\u00a0 &#8211;\u00a0 i\\sqrt{2} \\\\ \\text{ and } s = 4 + i\\sqrt{2}<\/span> Even when the answer will complex numbers, this method still works!<\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<div class=\"elementor-toggle-item\">\n\t\t\t\t\t<div id=\"elementor-tab-title-1155\" class=\"elementor-tab-title\" data-tab=\"5\" role=\"button\" aria-controls=\"elementor-tab-content-1155\" aria-expanded=\"false\">\n\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon elementor-toggle-icon-left\" aria-hidden=\"true\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon-closed\"><i class=\"fas fa-caret-right\"><\/i><\/span>\n\t\t\t\t\t\t\t\t<span class=\"elementor-toggle-icon-opened\"><i class=\"elementor-toggle-icon-opened fas fa-caret-up\"><\/i><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"elementor-toggle-title\" tabindex=\"0\"><span class=\"wp-katex-eq katex-display\" data-display=\"true\"> 2x^2  -  4x - 5 = 0 <\/span><\/a>\n\t\t\t\t\t<\/div>\n\n\t\t\t\t\t<div id=\"elementor-tab-content-1155\" class=\"elementor-tab-content elementor-clearfix\" data-tab=\"5\" role=\"region\" aria-labelledby=\"elementor-tab-title-1155\"><p>To answer this question, we first have to get it into a form we are familiar with. To do this, just divide the whole equation by 2. This gets us <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> x^2\u00a0 &#8211;\u00a0 2x\u00a0 &#8211;\u00a0 \\frac{5}{2} = 0 <\/span> We now find the roots <em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>such that <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> x^2 &#8211; 2x &#8211; \\frac{5}{2} = (x\u00a0 &#8211;\u00a0 r) (x\u00a0 &#8211;\u00a0 s) <\/span> Expanding this, we can find <em>r\u00a0<\/em>and\u00a0<em>s<\/em> by using the two equations <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r + s =\u00a0 2 \\\\ rs = -\\frac{5}{2} <\/span> Using the first equation, the average of <em>r\u00a0<\/em>and\u00a0<em>s <\/em>must be equal to 2\u00f72 = 1. Therefore we have <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r = 1\u00a0 &#8211;\u00a0 d \\text{ , } s = 1 + d <\/span> for some number <i>d.<\/i> Putting these equations of\u00a0<em>r\u00a0<\/em>and\u00a0<em>s\u00a0<\/em>into the 2nd property above, we get <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> (1\u00a0 &#8211;\u00a0 d) (1 + d) = -\\frac{5}{2} \\\\ 1\u00a0 &#8211;\u00a0 d^2 = -\\frac{5}{2} \\\\ d = \\sqrt{1 + \\frac{5}{2}} = \\sqrt{\\frac{7}{2}}\u00a0<\/span> So now we&#8217;ve found <em>d<\/em>. Substituting this value of\u00a0<em>d\u00a0<\/em>into the equations for\u00a0<em>r\u00a0<\/em>and\u00a0<em>s<\/em>, we find that our roots are <span class=\"wp-katex-eq katex-display\" data-display=\"true\"> r = 1\u00a0 &#8211;\u00a0 \\sqrt{\\frac{7}{2}} \\\\ \\text{ and } s = 1 + \\sqrt{\\frac{7}{2}} <\/span>\u00a0<\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-fe6eebf elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"fe6eebf\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-50276cd\" data-id=\"50276cd\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-7cd631a elementor-widget elementor-widget-heading\" data-id=\"7cd631a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-large\">Conclusion<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-137b820 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"137b820\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-78d8c6b\" data-id=\"78d8c6b\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-f602793 elementor-widget elementor-widget-text-editor\" data-id=\"f602793\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>I think this is a pretty interesting take on solving quadratics! Interesting enough to watch a 40min video on this (link to references). Whether we&#8217;ll start teaching this to young students, well I&#8217;ll just let Secretary of State for Education Gavin Williams decide (spread the word to get this post to him!). If you have any questions or found this to be a good read, feel free to leave a comment or just\u00a0<a href=\"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/contact\/\" target=\"_blank\" rel=\"noopener\">get in touch<\/a>!<\/p><p>This blog post was based of a YouTube video I watched by Po-Shen Loh. Check it out\u00a0<a href=\"https:\/\/www.youtube.com\/watch?v=XKBX0r3J-9Y&amp;t=453s&amp;ab_channel=DailyChallengewithPo-ShenLoh\" target=\"_blank\" rel=\"noopener\">here<\/a>!<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>Happy&nbsp;\u03c0-day! To celebrate, let&#8217;s go all the way back to GCSE maths where we just little baby kids, most likely annoying (at least I was), learning about quadratic equations. Say we want to solve the following quadratic: Solving this just means we want to find the values of x which makes the entire equation equal [&hellip;]<\/p>\n","protected":false},"author":22,"featured_media":1033,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"zakra_page_container_layout":"customizer","zakra_page_sidebar_layout":"customizer","zakra_remove_content_margin":false,"zakra_sidebar":"customizer","zakra_transparent_header":"customizer","zakra_logo":0,"zakra_main_header_style":"default","zakra_menu_item_color":"","zakra_menu_item_hover_color":"","zakra_menu_item_active_color":"","zakra_menu_active_style":"","zakra_page_header":true,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[10],"tags":[9],"class_list":["post-1027","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-backtobasics","tag-back-to-basics"],"_links":{"self":[{"href":"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/wp-json\/wp\/v2\/posts\/1027","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/wp-json\/wp\/v2\/users\/22"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/wp-json\/wp\/v2\/comments?post=1027"}],"version-history":[{"count":169,"href":"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/wp-json\/wp\/v2\/posts\/1027\/revisions"}],"predecessor-version":[{"id":1207,"href":"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/wp-json\/wp\/v2\/posts\/1027\/revisions\/1207"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/wp-json\/wp\/v2\/media\/1033"}],"wp:attachment":[{"href":"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/wp-json\/wp\/v2\/media?parent=1027"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/wp-json\/wp\/v2\/categories?post=1027"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lancaster.ac.uk\/stor-i-student-sites\/owen-li\/wp-json\/wp\/v2\/tags?post=1027"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}