Answer: x = 0, x = -3, x = 2
Explanation:
f(x) = x^3 + x^2 - 6x
f(x) = 0
x^3 + x^2 - 6x = 0
x(x^2 + x - 6) = 0
x = 0 or
x^2 + x - 6 = 0
D = b^2 - 4ac = 1 - 4*(-6) = 25
x = (-b - sqrt(D))/(2a) = (-1 - 5)/2 = -3 or
x = (-b + sqrt(D))/(2a) = (-1 + 5)/2 = 2