Question

Solve.

x3 + 0.9x2 − 0.9x = 0

Answer 1

I will assume you mean

x^3 + .9x^2 - .9x = 0

times 10
10x^3 + 9x^2 - 9x = 0
x(10x^2 + 9x - 9) = 0
x = 0 or x = (-9 ± √441)/20

x = 0 or x = (-9 ± 21 )/20
x = 0 or x = .6 or x = -1.5