Question

Решите все здания на фотографии. Пж

Answer 1

$1) \frac{ {a}^{2} + 9 }{(a - 3)(a + 3)} - \frac{a}{a + 3} = \\ \frac{ {a}^{2} + 9 - a(a - 3) }{(a - 3)(a + 3)} =$
$\frac{ {a}^{2} + 9 - {a}^{2} + 3a }{(a - 3)(a + 3)} = \frac{9 + 3a}{(a - 3)(a + 3)} =$
$\frac{3(3 + a)}{(a - 3)(a + 3)} = \frac{3}{a - 3}$
2.
${7x}^{2} + 9x + 2 = 0 \\ d = 81 - 4 \times 7 \times 2 = 81 - 56 = \\ 25 = 5$
$x1 = \frac{ - 9 + 5}{14} = \frac{ - 4}{14} = - \frac{2}{7}$
$x2 = \frac{ - 9 - 5}{14} = - \frac{14}{14} = - 1$
3.
$2x + 3y = - 7 \\ x = 4 + y \\ 2(4 + y) + 3y = - 7$
$8 + 2y + 3y = - 7 \\ 8 + 5y = - 7 \\ 5y = - 15 \\ y = - 3$
$x = 4 - 3 = 1$
7)
$26 > \sqrt{686}$
Остальное не знаю