Решите уравнения: а) б)

A) 12 - 6x² = (2x +3)(5-3x) 12- 6x² = 10x - 6x² + 15 - 9x 12- 6x² = -6x² + x + 15 -12x² + x - 3 = 0 | * (-1) 12x² - x + 3 = 0 D = 1 - 4*12*3 = 1 - 144 = -143 < 0, корней нет б)(x+7)(x-8) - (x-9)(x+10) = 0 (x²- 8x + 7x - 56) - (x² + 10x - 9x - 90) = 0 (x² - x - 56) - (x² + x - 90) = 0 x² - x - 56 - x² - x + 90 = 0 -2x + 34 = 0 -2x = -34 x = -34/-2 x = 17