посчитайте через дискриминант -x^2=5x-14

x1 = -7; x2 = 2

-x² = 5x - 14

-x² - 5x + 14 = 0

Д = b² - 4ac = 25 + 56 = 81 = 9²

x1 = (5 + 9) / -2 = -7

x2 = (5 - 9) / -2 = 2