Уравнение: -5x2 + 8x + 4 = 0.
Дискриминант D = b2 - 4ac = 82 - 4(-5)(4) = 64 + 80 = 144.
x1 = (-b + sqrt(D)) / 2a = (-8 + 12) / (2 * -5) = 4 / -10 = -0.4.
x2 = (-b - sqrt(D)) / 2a = (-8 - 12) / (2 * -5) = -20 / -10 = 2.