1^3 + 2^3 + 3^3 +4^3 ... n^3 = ?

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Question from ireimaima, a student:

Hi..
Can u please help me with this question..
I find that when i test eg: n=2 for n (n+1) /4,
it seems that it does not giving me the right answer of 1^3 + 2^3 = 9
but 3/2... i'm confuse..can u please help me..thanks so much

Prove that:
1^3 + 2^3 + 3^3 +4^3 ... n^3 = n (n+1) /4

Ireimaima,

You are correct the expression you have is not correct It should be

1³ + 2³ + 3³ + 4³ ... n³ = [n (n+1) /2]²

Now can you prove it by induction?

Penny

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