document.write( "Question 1149333: 1^2+3^2+...+(2n-1)^2=1/3n(4n^2-1) \n" ); document.write( "
Algebra.Com's Answer #770678 by math_helper(2461)\"\" \"About 
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\n" ); document.write( "n=1: \"1%5E2+=+1+\" & \"%281%2F3%29%281%29%284%281%29%5E2-1%29+=+%281%2F3%29%283%29+=+1+\"\r
\n" ); document.write( "\n" ); document.write( "Assume \"1%5E2%2B2%5E2+\" + ... + \"+%282n-1%29%5E2+\" = \"%281%2F3%29%28n%29%284n%5E2-1%29\" for n=k\r
\n" ); document.write( "\n" ); document.write( "Let n=k+1:\r
\n" ); document.write( "\n" ); document.write( " \"1%5E2%2B2%5E2+\" + ... + \"+%282k-1%29%5E2+\" + \"+%282%28k%2B1%29-1%29%5E2+\"\r
\n" ); document.write( "\n" ); document.write( "// Apply hypothesis to all but the last term
\n" ); document.write( "= \"+%281%2F3%29%28k%29%284k%5E2-1%29+\" + \"+%282%28k%2B1%29-1%29%5E2+\"\r
\n" ); document.write( "\n" ); document.write( "// combine
\n" ); document.write( "= \"+%281%2F3%29%284k%5E3%2B12k%5E2%2B11k%2B3%29+\"\r
\n" ); document.write( "\n" ); document.write( "// Here you can attempt to factor, or, you can see if (1/3)(k+1)(4(k+1)^2-1)
\n" ); document.write( "// expands to the same expression... I will do the latter approach...\r
\n" ); document.write( "\n" ); document.write( "\"+%281%2F3%29%28k%2B1%29%284%28k%2B1%29%5E2-1%29+\"
\n" ); document.write( "= \"+%281%2F3%29%28k%2B1%29%284k%5E2%2B8k%2B4-1%29+\"
\n" ); document.write( "= \"+%281%2F3%29%28k%2B1%29%284k%5E2%2B8k%2B3%29+\"
\n" ); document.write( "= \"+%281%2F3%29%284k%5E3%2B8k%5E2%2B3k%2B4k%5E2%2B8k%2B3%29+\"
\n" ); document.write( "= \"+%281%2F3%29%284k%5E3%2B12k%5E2%2B11k%2B3%29+\"\r
\n" ); document.write( "\n" ); document.write( "They match, the hypothesis is also true for n=k+1, DONE.
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