f(x) = (6x^2 - 1) cos x, maka f'(x) adalah....

f(x) = (6x² - 1) cos x
f'(x) = (12x)(cos x) + (6x² - 1)(-sin x)
       = 12x cos x - (6x² - 1) sin x

turunan

f(x) =  (6x² -1) cos x
f(x)= u(x)/v(x)
u = 6x²-1 -->u' = 12x
v = cos x --> v' = - sin x

f ' (x) =  ( u'v +uv')
f ' (x) = 12x cos x  + (6x² -1)( - sin x)
f ' (x) = 12x.cos x -  (6x² - 1) sin x