вправа 450 гдз 7 клас алгебра Мерзляк Полонський

Відповідь:

1) (2x - 9)(x + 6) - x(x + 6) = 0;
(x + 6)(2x - 9 - x) = 0;
(x + 6)(x - 9) = 0;
x + 6 = 0;
x = -6;
x - 9 = 0;
x = 9;
2) (3x + 4)(x - 10) + (10 - x)(x - 8) = 0;
(3x + 4)(x - 10) - (x - 10)(x - 8) = 0;
(x - 10)(3x + 4 - (x - 8)) = 0;
(x - 10)(3x + 4 - x + 8) = 0;
(x - 10)(2x + 12) = 0;
x - 10 = 0;
x = 10;
2x + 12 = 0;
x = -6;
3) 3(3x + 1)² - 4(3x + 1) = 0;
(3x + 1)(3(3x + 1) - 4) = 0;
(3x + 1)(9x + 3 - 4) = 0;
(3x + 1)(9x - 1) = 0;
3x + 1 = 0; \begin{equation}x=-\frac{1}{3};\end{equation} 9x - 1 = 0; \begin{equation}x=\frac{1}{9};\end{equation} 4) (9x - 12) - x(9x - 12) = 0;
(9x - 12)(1 - x) = 0;
9x - 12 = 0; \begin{equation}x=1\frac{1}{3};\end{equation} 1 - x = 0;
x = 1.