What are the roots of the cubic equcation x^{3}-8x-3=0?

Ans: D. x=-2.62, -0.38, 3

1. step

x= x^{3}-8x-3^{2}+3x-1 By inspection +3 is a root, and x-3 is a factor. Factor out (x-3)

x-3

Please do whole the problem. How did they get x^{2}+3x-1=0