If a quadratic equation does not factor in a way that makes the equation easy to factor, you can solve the equation with the quadratic formula. Below I will put the equation into the right form for the quadratic formula, then plug it in and solve. (+- means plus or minus)
9x^2 - 12x + 4 = 17
9x^2 - 12x - 13 = 0
x = (-(-12) +- sqrt((-12)^12 - 4(9)(-13))) / 2(9)
x = (12 +- sqrt(144 + 468)) / 18
x1 = 2.041
x2 = -0.708
These are the two answers to the equation. The quadratic formula is very messy to solve in this text box, but if you would like more work shown let me know and I will fill in the steps of calculations I skipped over.