Carilah f' (x) dari 1- x²/1+x²...

Turunan

f(x) = (1 - x²) / (1 + x²)
u = 1 - x² ---> u' = -2x
v = 1 + x² --> v' = 2x

f  = u/v --> f '  = u'v - uv'/ (v²)

f '(x) = { -2x(1+x²) - (1-x²)(2x)} / (1+ x²)²
f '(x) = { -2x - 2x³ - 2x + 2x³) / (1 + x²)²
f '(x) =  - 4x/ (1 + x²)²