вправа 548 гдз 7 клас алгебра Мерзляк Полонський

Відповідь:

1) (3x - 5)² - 49 = 0;
(3x - 5 - 7)(3x - 5 + 7) = 0:
(3x - 12)(3x + 2) = 0;
3x - 12 = 0;
x = 4;
3x + 2 = 0; \begin{equation}x=-\frac{2}{3};\end{equation} 2) (4x + 7)² - 9x² = 0;
(4x + 7 - 3x)(4x + 7 + 3x) = 0;
(x + 7)(7x + 7) = 0;
x + 7 = 0;
x = -7;
7x + 7 = 0;
x = -1;
3) (a - 1)² - (2a + 9)² = 0;
((a - 1) - (2a + 9))((a -
- 1) + (2a + 9)) = 0;
(-a - 10)(3a + 8) = 0;
a + 10 = 0;
a = -10;
3a + 8 = 0; \begin{equation}a=-2\frac{2}{3};\end{equation} 4) 25(3b + 1)² - 16(2b - 1)² = 0;
(5(3b + 1) - 4(2b - 1))(5(3b +
+ 1) + 4(2b - 1)) = 0;
(15b + 5 - 8b + 4)(15b +
+ 5 + 8b - 4) = 0;
(7b + 9)(23b + 1) = 0;
7b + 9 = 0; \begin{equation}b=-1\frac{2}{7};\end{equation} 23b + 1 = 0; \begin{equation}b=-\frac{1}{23}.\end{equation}