№3. Решить уравнение: a) (x - 4)(x + 2) - (x - 5)(x + 6) = - x, б) (3x + 5)(2x + 1) = (6x + 5)(x - 3) + 7.

№3. Решить уравнение:

a) $$(x - 4)(x + 2) - (x - 5)(x + 6) = -x;$$

$$x^2 - 4x + 2x - 8 - (x^2 - 5x + 6x - 30) = -x;$$

$$x^2 - 2x - 8 - x^2 - x + 30 = -x;$$

$$-3x + 22 = -x;$$

$$-3x + x = -22;$$

$$-2x = -22;$$

$$x = 11 $$.

Ответ: $$x = 11 $$.

б) $$(3x + 5)(2x + 1) = (6x + 5)(x - 3) + 7;$$

$$6x^2 + 10x + 3x + 5 = 6x^2 + 5x - 18x - 15 + 7;$$

$$6x^2 + 13x + 5 = 6x^2 - 13x - 8;$$

$$6x^2 - 6x^2 + 13x + 13x = -8 - 5;$$

$$26x = -13;$$

$$x = -\frac{13}{26};$$

$$x = -\frac{1}{2} $$.

Ответ: $$x = -\frac{1}{2} $$.