3. x² - 11x + 30 = 0

a = 1, b = -11, c = 30 D = (-11)² - 4 * 1 * 30 = 121 - 120 = 1 x₁ = (11 + √1) / 2 * 1 = (11 + 1) / 2 = 12 / 2 = 6 x₂ = (11 - √1) / 2 * 1 = (11 - 1) / 2 = 10 / 2 = 5 Ответ: x₁ = 6, x₂ = 5