If f(x)=1/x^2 find f'(x) using the definition of the derivative.

(note: If you instead use the power rule, f'(x)=nx^(n-1), you will get zero credit for this problem. It is useful check of your answer though.)

The answer is -2/x^3 and the best I can get is -1/x^3.

Could someone get me on the right track? If you can't help by tomorrow, don't bother because it is due tomorrow.

Thanks!