Question

ПОМОГИТЕ ПЖ ДАЮ 50 БАЛЛОВ
$\left( {\frac{1}{{a + 5}} - \frac{1}{{a - 5}}} \right):\frac{5}{{a + 5}}$

Answer 1

$( \frac{1}{a + 5} - \frac{1}{a - 5} ) \div \frac{5}{a + 5} =\\ \frac{a - 5 - (a + 5)}{(a + 5) \times (a - 5)} \div \frac{5}{a + 5} =\\ \frac{a - 5 - a - 5}{(a + 5) \times (a - 5)} \div \frac{5}{a + 5} = \\ - \frac{ 10}{(a + 5) \times (a - 5)} \div \frac{5}{a + 5} = - \frac{2}{a - 5}$