7. x² - x - 12 = 0

a = 1, b = -1, c = -12 D = (-1)² - 4 * 1 * (-12) = 1 + 48 = 49 x₁ = (1 + √49) / 2 * 1 = (1 + 7) / 2 = 8 / 2 = 4 x₂ = (1 - √49) / 2 * 1 = (1 - 7) / 2 = -6 / 2 = -3 Ответ: x₁ = 4, x₂ = -3