Question

A plus B minus 1
$(a + b) {}^{ - 1} (a {}^{ - 1} + b {}^{ - 1} ) = (ab) {}^{ - 1}$

Answer 1

$\frac{1}{a + b} \times ( \frac{1}{a} + \frac{1}{b} ) \\ = \frac{1}{(a + b)} \times \frac{(a + b)}{ab} \\ = \frac{1}{ab} \\ {ab}^{ - 1} proved$