f'（x）=1/3*3x²-21*2x=x²－42x令f'(x)=0得 x²－42x＝0 ∴ x=0或x＝42f(0)=1,f(42)=-12347f(-1)=1/3(-1)³-21(-1)²+1=-1/3-21+1=-62/3f(4)=1/3*4³-21*4²+1=-941/3∴最大值是1,最...