Решите уравнение: (x-9)²=-x²+15x+50

(x -9)(x - 9) = -x² + 15x + 50
x² - 9x - 9x + 81 = - x² + 15x + 50
x² - 18x + 81 + x² - 15x - 50 = 0
2x² - 33x + 31 = 0
D = b² - 4ac = ( - 33)² - 4 × 2 × 31 = 1089 - 248 = 841 = 29²
x₁ = 33 + 29 / 2 × 2 = 62 /4 = 15,5
x₂ = 33 - 29 / 4 = 4 / 4 = 1