3 Решите уравнение: a) (3x - 4)(3x + 4) - 9x(x + 2) = 20; 6) 12,5y (2y + - 11 = (5y – 6) (5y + 6). 1 5

Решим задание Вариант 2, задание 3.

a) $$(3x - 4)(3x + 4) - 9x(x + 2) = 20 $$

$$9x^2 - 16 - 9x^2 - 18x = 20 $$

$$-18x = 20 + 16 $$

$$-18x = 36 $$

$$x = -2 $$.

б) $$12,5y\left(2y + \frac{1}{5}\right) - 11 = (5y - 6)(5y + 6) $$.

$$25y^2 + \frac{12,5}{5}y - 11 = 25y^2 - 36 $$

$$2.5y = -36 + 11 $$

$$2.5y = -25 $$

$$y = -10 $$.

Ответ: a) $$x = -2 $$, б) $$y = -10 $$.