#### Answer

$(\sqrt{x}-y)(\sqrt{x}+y)=x-y^{2}$

#### Work Step by Step

$(\sqrt{x}-y)(\sqrt{x}+y)$
Evaluate this product by using the formula for factoring a difference of squares. The formula is $a^{2}-b^{2}=(a-b)(a+b)$. For this expression, $a=\sqrt{x}$ and $b=y$
Substitute the known values into the formula and simplify if possible:
$(\sqrt{x}-y)(\sqrt{x}+y)=(\sqrt{x})^{2}-y^{2}=x-y^{2}$