For what values ofathere are exactly two real numbers that satify the equation:

x^3 + (a-1)x^2 + (9-a)x - 9 = 0

Find all possible answers.

Firstly this is what I have done.

I expand and group which leaves me with:

(x^3 - x^2) + a(x^2 - x) + 9(x - 1) = 0

Then I divide by (x-1) to get x^2 + ax + 9 = 0

Then from there I am lost, would love to know how to finish it off. Thanks!