Question

только 2 и 4 задание​

Answer 1

2)

$frac{m - n}{ (n - m) {}^{2} } = frac{m - n}{(n - m)(n - m)} = frac{1}{n - m}$

4)

$frac{a {}^{2} - 1 }{(a - 1) {}^{2} } = frac{(a - 1)(a + 1)}{(a - 1)(a - 1)} = frac{a + 1}{a - 1}$