f(x)=x^3-x^2-x-1
f(2)=8-4-2-1=1
f'(x)=3x^2-2x-1
f'(2)=12-2-1=9
切线:y=9x+b
1=9*2+b
b=-17
切线:y=9x-17
f'(x)=3x^2-2x-1=0
x=1,x=-1/3
x1
f(x)=x^3-x^2-x-1
f(2)=8-4-2-1=1
f'(x)=3x^2-2x-1
f'(2)=12-2-1=9
切线:y=9x+b
1=9*2+b
b=-17
切线:y=9x-17
f'(x)=3x^2-2x-1=0
x=1,x=-1/3
x1