#### Answer

$-1/(w-4); w \ne 4$

#### Work Step by Step

In order to simplify this expression, we need something to be in the numerator and the denominator of the fraction so it can be canceled out. Therefore, we factor and obtain:
$(-1)(w-4) / (w-4)(w-4) \\\\ -1/(w-4)$
w cannot equal 4, for if this were the case, the denominator of the fraction would cancel out to 0, which is not allowed.