f(x)=2+18x-15x^2-4x^3,
f'(x)=18-30x-12x^2,
f'(x)=0, 18-30x-12x^2=0,
6x^2+15x-9=0,
D=441,
x1=-3,
x2=1/2.
f(x)=2+18x-15x^2-4x^3,
f'(x)=18-30x-12x^2,
f'(x)=0, 18-30x-12x^2=0,
6x^2+15x-9=0,
D=441,
x1=-3,
x2=1/2.