f(x)=x^3-6x^2+9x-3
f'(x)=3x^2-12x+9
=3(x^2-4x+3)
=3(x-1)(x-3)
令f'(x)=0得x1=1,x2=3
隨x變化,f'(x),f(x)變化如下：
x (-∞,1) 1 (1,3) 3 (3,+∞)
f'(x) + 0 - 0 +
f(x) 增 極大 減 極小 減
f(x)極大值=f(1)=1
f(x)極小值=f(3)=27-54+27-3=-3