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