jika f(x) = 5x-4 per 5x+4 maka turunan fungsi f di nol adalah

f(x) = 5x-4/5x+4
misal
u = 5x-4 maka u' = 5
v = 5x + 4 maka v' = 5

f'(x) = u'v - uv'/v^2
f'(x) = 5(5x+4) - (5x-4)5 / (5x+4)^2
f'(x) = 25x + 20 - 25x + 20 / (5x+4)^2
f'(x) = 40/(5x+4)^2
f'(0) = 40/(5.0+4)^2
f'(0) = 40/16 = 5/2 = 2 1/2