f'(x) = lim(h→0) (f(x+h)-f(x))/h
= lim(h→0) ((x+h)^n - x^n) / h
= lim(h→0) (x^n + nx^n-1h +...+h^n - x^n)/h
= lim(h→0) (nx^n-1+ ...+h^n-1)
= nx^n-1
f'(x) = lim(h→0) (f(x+h)-f(x))/h
= lim(h→0) ((x+h)^n - x^n) / h
= lim(h→0) (x^n + nx^n-1h +...+h^n - x^n)/h
= lim(h→0) (nx^n-1+ ...+h^n-1)
= nx^n-1