fungsi f(x)= (x-2) (x^2-4x+1) naik pada interval tolong bantu jawab ..

f(x) = (x-2)(x²-4x+1)
= x³-4x²+x-2x²+8x-2
= x³-6x²+9x-2
f'(x) < 0
3x² - 12x + 9 < 0

3(x²-4x+3)=0
(x-3)(x-1)=0
x=3 x =1
interval naik 1<x<3