#### Answer

$x=-7$ or $x=9$

#### Work Step by Step

A rational expression is undefined when the value of its denominator is zero. Write and solve an expression where the denominator is zero.
$(x+7)(x-9)=0$
A product is zero when either factor is zero.
$x+7=0$ or $x-9=0$
Use the addition property of equality to solve both equations for x.
$x+7-7=0-7$ or $x-9+9=0+9$
Simplify.
$x=-7$ or $x=9$