Given that f : x -> x^2 + 6x, and g: x -> 2x - 1 ... where x is a real number.

Find the two values of x such that fg(x) = gf(x), giving each answer in the form $\displaystyle p + q \sqrt{3}$

I have tried solving it by equating by solving it for both of the functions but that's not working. How should I proceed with it?