jika f(x)= minus 2 per akar x maka f(x) +2x.f aksen(x)..

f(x)= -2 / √x
f(x)= -2 x⁻¹/²
f'(x)=  x ⁻³/²
f '(x)= 1/(x³/²)
f'(x) =  1/(x√x)
.
f(x) + 2x. f'(x)=  -2/(√x)  + 2x / (x√x)
f(x) + 2x . f '(x)= ( - 2x  + 2x)/(x√x) = 0/(x√x)
f(x) + 2x. f '(x)=  0