{"id":1357,"date":"2016-07-21T10:16:22","date_gmt":"2016-07-21T10:16:22","guid":{"rendered":"http:\/\/www.testingdocs.com\/questions\/?p=1357"},"modified":"2024-12-13T15:11:45","modified_gmt":"2024-12-13T15:11:45","slug":"sum-of-n-natural-number-squares","status":"publish","type":"post","link":"https:\/\/www.testingdocs.com\/questions\/sum-of-n-natural-number-squares\/","title":{"rendered":"Mathematical Induction : Sum of N natural number squares"},"content":{"rendered":"<h2>Mathematical Induction : Sum of N natural number squares<\/h2>\n<p>Using <a href=\"https:\/\/www.testingdocs.com\/questions\/what-is-mathematical-induction\/\">Mathematical Induction<\/a> Prove that the sum of the first n natural number squares is:<\/p>\n<p>&nbsp;<\/p>\n<p><img decoding=\"async\" src=\"http:\/\/latex.codecogs.com\/gif.latex?\\LARGE&amp;space;\\sum_{1}^{n}i^{2}=&amp;space;\\frac{n(n+1)(2n+1)}{6}\" alt=\"\\LARGE \\sum_{1}^{n}i^{2}= \\frac{n(n+1)(2n+1)}{6}\" align=\"absmiddle\" title=\"\"><\/p>\n<p>i.e<\/p>\n<h3><\/h3>\n<h3><img decoding=\"async\" src=\"http:\/\/latex.codecogs.com\/gif.latex?\\LARGE&amp;space;1^2&amp;space;+&amp;space;2^2&amp;space;+&amp;space;3^2&amp;space;+&amp;space;...&amp;space;+&amp;space;n^2&amp;space;=&amp;space;\\frac{n(n+1)(2n+1)}{6}\" alt=\"\\LARGE 1^2 + 2^2 + 3^2 + ... + n^2 = \\frac{n(n+1)(2n+1)}{6}\" align=\"absmiddle\" title=\"\"><\/h3>\n<p>Using WolframAlpha to find the formula. WolframAlpha is a great mathematical computational tool for Mathematical students.<\/p>\n<ul>\n<li><strong>https:\/\/www.wolframalpha.com\/<\/strong><\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2027\" src=\"http:\/\/www.testingdocs.com\/questions\/wp-content\/uploads\/WolframAlpha_Sum_of_Squares.png\" alt=\"WolframAlpha_Sum_of_Squares\" width=\"1242\" height=\"547\" title=\"\"><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h2>Proof<\/h2>\n<p>By Mathematical Induction.<\/p>\n<h3>Base case : P(1)<\/h3>\n<p>Let&#8217;s prove that the base case holds true. We need to show that P(1) is true.<\/p>\n<p><img decoding=\"async\" src=\"http:\/\/latex.codecogs.com\/gif.latex?\\LARGE&amp;space;1^2&amp;space;=&amp;space;\\frac{1*(1+1)(2*1+1)}{6}\" alt=\"\\LARGE 1^2 = \\frac{1*(1+1)(2*1+1)}{6}\" align=\"absmiddle\" title=\"\"><\/p>\n<p><img decoding=\"async\" src=\"http:\/\/latex.codecogs.com\/gif.latex?\\LARGE&amp;space;1^2&amp;space;=&amp;space;\\frac{1.2.3}{6}\" alt=\"\\LARGE 1^2 = \\frac{1.2.3}{6}\" align=\"absmiddle\" title=\"\"><\/p>\n<p>1=1<\/p>\n<p>P(1) is true.<\/p>\n<h3>Induction Case<\/h3>\n<p>Let&#8217;s assume that P(k) hold true. Assume that for some positive k, P(k) holds true, so that<\/p>\n<p>P(k)<\/p>\n<p><img decoding=\"async\" src=\"http:\/\/latex.codecogs.com\/gif.latex?\\LARGE&amp;space;\\sum_{1}^{k}&amp;space;i^{2}&amp;space;=\\frac{k(k+1)(2k+1)}{6}\" alt=\"\\LARGE \\sum_{1}^{k} i^{2} =\\frac{k(k+1)(2k+1)}{6}\" align=\"absmiddle\" title=\"\"><\/p>\n<p>We need to show that P(k + 1) holds true.<\/p>\n<p><img decoding=\"async\" src=\"http:\/\/latex.codecogs.com\/gif.latex?\\LARGE&amp;space;\\sum_{1}^{k+1}i^2&amp;space;=&amp;space;\\sum_{1}^{k}i^2&amp;space;+&amp;space;(k+1)^2\" alt=\"\\LARGE \\sum_{1}^{k+1}i^2 = \\sum_{1}^{k}i^2 + (k+1)^2\" align=\"absmiddle\" title=\"\"><\/p>\n<p>We have assumed that P(k) is true. Replacing\u00a0 for k terms we get:<\/p>\n<p><img decoding=\"async\" src=\"http:\/\/latex.codecogs.com\/gif.latex?\\LARGE&amp;space;=&amp;space;\\frac{k(k+1)(2k+1)}{6}&amp;space;+&amp;space;(k+1)^2\" alt=\"\\LARGE = \\frac{k(k+1)(2k+1)}{6} + (k+1)^2\" align=\"absmiddle\" title=\"\"><\/p>\n<p>Taking (k+1) common we get :<\/p>\n<p><img decoding=\"async\" src=\"http:\/\/latex.codecogs.com\/gif.latex?\\LARGE&amp;space;=&amp;space;\\frac{(k+1)(k(2k+1)&amp;space;+&amp;space;6(k+1))}{6}\" alt=\"\\LARGE = \\frac{(k+1)(k(2k+1) + 6(k+1))}{6}\" align=\"absmiddle\" title=\"\"><\/p>\n<p>Take hints in the factorization, we need to prove and eventually get (k+1) in terms of k.<\/p>\n<p>expand and rearrange the 2nd term:<\/p>\n<p><img decoding=\"async\" src=\"http:\/\/latex.codecogs.com\/gif.latex?\\LARGE&amp;space;=&amp;space;\\frac{(k+1)(2k^2&amp;space;+&amp;space;k&amp;space;+&amp;space;6k&amp;space;+&amp;space;6)}{6}\" alt=\"\\LARGE = \\frac{(k+1)(2k^2 + k + 6k + 6)}{6}\" align=\"absmiddle\" title=\"\"><\/p>\n<p><img decoding=\"async\" src=\"http:\/\/latex.codecogs.com\/gif.latex?\\LARGE&amp;space;\\frac{(k+1)(2k^2&amp;space;+&amp;space;4k&amp;space;+&amp;space;6&amp;space;+&amp;space;3k)}{6}\" alt=\"\\LARGE \\frac{(k+1)(2k^2 + 4k + 6 + 3k)}{6}\" align=\"absmiddle\" title=\"\"><\/p>\n<p><img decoding=\"async\" src=\"http:\/\/latex.codecogs.com\/gif.latex?\\LARGE&amp;space;=&amp;space;\\frac{(k+1)(2k(k+2)&amp;space;+&amp;space;3(k+2))}{6}\" alt=\"\\LARGE = \\frac{(k+1)(2k(k+2) + 3(k+2))}{6}\" align=\"absmiddle\" title=\"\"><\/p>\n<p>Taking k+2 common<\/p>\n<p><img decoding=\"async\" src=\"http:\/\/latex.codecogs.com\/gif.latex?\\LARGE&amp;space;=&amp;space;\\frac{(k+1)(k+2)(2k+3)}{6}\" alt=\"\\LARGE = \\frac{(k+1)(k+2)(2k+3)}{6}\" align=\"absmiddle\" title=\"\"><\/p>\n<p><img decoding=\"async\" src=\"http:\/\/latex.codecogs.com\/gif.latex?\\LARGE&amp;space;=&amp;space;\\frac{(k+1)((k+1)+1)(2(k+1)+1)}{6}\" alt=\"\\LARGE = \\frac{(k+1)((k+1)+1)(2(k+1)+1)}{6}\" align=\"absmiddle\" title=\"\"><\/p>\n<p>&nbsp;<\/p>\n<p>Hence P(k + 1) holds true, when P(k) is true, so P(n) is true for all finite natural numbers n.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Mathematical Induction : Sum of N natural number squares Using Mathematical Induction Prove that the sum of the first n natural number squares is: &nbsp; i.e Using WolframAlpha to find the formula. WolframAlpha is a great mathematical computational tool for Mathematical students. https:\/\/www.wolframalpha.com\/ &nbsp; &nbsp; &nbsp; Proof By Mathematical Induction. Base case : P(1) Let&#8217;s [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[849],"tags":[],"class_list":["post-1357","post","type-post","status-publish","format-standard","hentry","category-math-questions","has-post-title","has-post-date","has-post-category","has-post-tag","has-post-comment","has-post-author",""],"_links":{"self":[{"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/posts\/1357","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/comments?post=1357"}],"version-history":[{"count":17,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/posts\/1357\/revisions"}],"predecessor-version":[{"id":26308,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/posts\/1357\/revisions\/26308"}],"wp:attachment":[{"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/media?parent=1357"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/categories?post=1357"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.testingdocs.com\/questions\/wp-json\/wp\/v2\/tags?post=1357"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}