Помогите!

Вычислите f'(1), если
f(x) = [tex] \frac{2x^{2}+4}{x^{2}} [/tex]

f'(x) = [ 4x*x^2 -(2x^2+4)*2x ] /x^4 = [ 4x^3-4x^3-8x ] /x^4 =-8x/x^4= -8/x^3

f'(1) = -8/1 =-8