4x^2 - 2x = 3x + 6
4x^2 - 5x - 6 = 0
D = 25 + 96 = 121
X1 = (5 - 11) / 8 = -0.75
X2= (5 + 11) / 8 = 2
X^2 + 2X - 15 = 0
D = 4 + 60 = 64
X1 = (-2 - 8) / 2 = -5
X2 = (-2 + 8) / 2 = 3