Question

How do you simplify `(a^-1 + b^-1)^-1`?

Answer 1

`(ab)/(a+b)`

Explanation:

The power of -1 means find the reciprocal (i.e. 1 divided by the value)

Write `a^-1` as `1/a` and `b^-1` as `1/b`

Then:
`(1/a+1/b)^-1 = ((a+b)/(ab))^-1 = (ab)/(a+b)`