document.write( "Question 1184007: prove by mathematical induction:
\n" ); document.write( "1^5 + 2^5 + 3^5 + ... + n^5 = (1/12)n^2(n+1)^2(2n^2 + 2n -1)
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Algebra.Com's Answer #814546 by math_helper(2461)\"\" \"About 
You can put this solution on YOUR website!
prove by mathematical induction:
\n" ); document.write( "1^5 + 2^5 + 3^5 + ... + n^5 = (1/12)n^2(n+1)^2(2n^2 + 2n -1)
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\n" ); document.write( "Base case: \"1%5E5\" = 1
\n" ); document.write( " \"%281%2F12%29%281%29%5E2%281%2B1%29%5E2%282%281%29%5E2%2B2%281%29-1%29+\" = \"%281%2F12%29%284%29%283%29\" = 1\r
\n" ); document.write( "\n" ); document.write( "Base case holds.\r
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\n" ); document.write( "\n" ); document.write( "Hypothesis:
\n" ); document.write( "Assume \"1%5E5+%2B+2%5E5+%2B+3%5E5\" + ... + \"n%5E5\" = \"+%281%2F12%29n%5E2%28n%2B1%29%5E2%282n%5E2+%2B+2n+-1%29+\" for n=k. (*)\r
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\n" ); document.write( "\n" ); document.write( "Step case: Let n=k+1
\n" ); document.write( " [ \"+1%5E5+%2B+2%5E5+%2B+3%5E5\" + ... + \"k%5E5\" ] + \"%28k%2B1%29%5E5\" \r
\n" ); document.write( "\n" ); document.write( "... use hypothesis on terms within [ ] ...\r
\n" ); document.write( "\n" ); document.write( "= \"+%281%2F12%29k%5E2%28k%2B1%29%5E2%282k%5E2+%2B+2k+-1%29+\" + \"+%28k%2B1%29%5E5\"\r
\n" ); document.write( "\n" ); document.write( "... this reduces to (you can factor \"%28k%2B1%29%5E2\" then use a factoring website for the rest) ... (see NOTE)\r
\n" ); document.write( "\n" ); document.write( "= \"+%281%2F12%29%28k%2B1%29%5E2%28%28k%2B2%29%5E2%282k%5E2%2B6k%2B3%29%29+\"\r
\n" ); document.write( "\n" ); document.write( "The proof is complete here, but it is not obvious, so
\n" ); document.write( "let u=k+1 --> k=u-1\r
\n" ); document.write( "\n" ); document.write( "= \"+%281%2F12%29%28u%29%5E2%28u%2B1%29%5E2%282%28u-1%29%5E2%2B6%28u-1%29%2B3%29+\"
\n" ); document.write( "= \"+%281%2F12%29%28u%29%5E2%28u%2B1%29%5E2%282u%5E2%2B2u-1%29+\"\r
\n" ); document.write( "\n" ); document.write( "Proof complete\r
\n" ); document.write( "\n" ); document.write( "NOTE: I admit, there may be an easier path here. If other tutors (or the student) wish to find it, more power to them. I gave the general idea...\r
\n" ); document.write( "\n" ); document.write( "If this helps the student, thanks are appreciated.
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