Answer
$ -h$.
Work Step by Step
The given expression is
$\Rightarrow x(x+h)\left ( \frac{1}{x+h} -\frac{1}{x}\right )$
Apply the distributive property.
$\Rightarrow x(x+h)\cdot \frac{1}{x+h} -x(x+h)\cdot \frac{1}{x}$
Cancel common terms.
$\Rightarrow x -(x+h)$
Simplify.
$\Rightarrow x -x-h$
$\Rightarrow -h$.
