Question

1^2+2^2+....+n^2=n(n+1)(2n+1)÷6;
prove it.

Answer 1

1-2-2-2-3-2-n-2-1-6n-n-1-2n-1
Can you prove that 1^2+2^2+3^2+...+n^2=1/6n(n+1)(2n+1)? |