quadratics

(3x + 2)^2 - (8 * 9) = -4x           expand L side

9x^2 + 12x + 4   - 72 = - 4x       simplify

9x^2 + 16x -68 = 0

a = 9      b = 16       c = - 68

$x = {-b \pm \sqrt{b^2-4ac} \over 2a}$

$x = {-16 \pm \sqrt{16^2-4(9)(-68)} \over 2(9)}$       Plug and chug !