Odpowiedź :
x² + 3x = 2x + 6
x² + 3x - 2x - 6 = 0
x² + x - 6 = 0
a = 1, b = 1, c = -6
∆ = b² - 4ac
∆ = 1² - 4 * 1 * (-6) = 25
√∆ = √25 = 5
x = (-1 - 5)/(2 * 1) = -6/2 = -3
x = (-1 + 5)/(2 * 1) = 4/2 = 2
2(x + 3) = 12 + x
2x + 6 = 12 + x
2x - x = 12 - 6
x = 6