document.write( "Question 393642: Use mathematical induction to prove that
\n" ); document.write( "1^3+2^3+3^3+....+n^3=(1+2+3+....+n)^2\r
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Algebra.Com's Answer #279525 by richard1234(7193)\"\" \"About 
You can put this solution on YOUR website!
The base case \"1%5E3+=+1%5E2\" satisfies. Now, suppose that\r
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\n" ); document.write( "\n" ); document.write( "\"sum%28i%5E3%2C+i+=+1%2C+n%29+=+%28sum%28i%2C+i+=+1%2C+n%29%29%5E2\" for arbitrary n. We wish to prove that this implies the \"n%2B1\" case will be true, or that\r
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\n" ); document.write( "\n" ); document.write( "\"sum%28i%5E3%2C+i+=+1%2C+n%2B1%29+=+%28sum%28i%2C+i+=+1%2C+n%2B1%29%29%5E2\"\r
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\n" ); document.write( "\n" ); document.write( "We can show this is true, using the fact that and \"%28sum%28i%2C+i+=+1%2C+n%2B1%29%29%5E2+=+%28%28n%2B1%29%28n%2B2%29%2F2%29%5E2\" Therefore this is equivalent to showing that\r
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\n" ); document.write( "\n" ); document.write( "\"%28%28n%28n%2B1%29%29%2F2%29%5E2+%2B+%28n%2B1%29%5E3+=+%28%28n%2B1%29%28n%2B2%29%2F2%29%5E2\" \r
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\n" ); document.write( "\n" ); document.write( "Divide both sides by \"%28n%2B1%29%5E2\"\r
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\n" ); document.write( "\n" ); document.write( "\"n%5E2%2F4+%2B+%28n%2B1%29+=+%28%28n%2B2%29%2F2%29%5E2\"\r
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\n" ); document.write( "\n" ); document.write( "\"%28n%5E2+%2B+4n+%2B+4%29%2F4+=+%28n%5E2+%2B+4n+%2B+4%29%2F4\"\r
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\n" ); document.write( "\n" ); document.write( "This holds for all n, so the statement holds for n+1. The induction is complete, so \"sum%28i%5E3%2C+i+=+1%2C+n%29+=+%28sum%28i%2C+i+=+1%2C+n%29%29%5E2\"\r
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