Question

срочно, пожалуйста, очень нужно

Answer 1

Ответ:

$( \frac{3a}{ {a}^{2} - 36 } - \frac{6}{5a + 30} ) \div \frac{27}{ {a}^{2} - 36} = \\ = ( \frac{3a}{(a - 6)(a + 6)} - \frac{6}{5(a + 6)} ) \times \frac{(a - 6)(a + 6) }{27} = \\ = \frac{3a \times 5 - 6(a - 6)}{5(a - 6)(a + 6)} \times \frac{(a - 6)(a + 6)}{27} = \\ = \frac{15a - 6a + 36}{5(a - 6)(a +6 )} \times \frac{(a - 6)(a + 6)}{27} = \\ = \frac{9(a + 4)}{5} \times \frac{1}{27} = \frac{a + 4}{5}$

при а=-1

$\frac{ - 1 + 4}{5} = - \frac{3}{5}$