Simplify 3 square root of xy- square root of 9xy

$3 \sqrt{x y} - \sqrt{9 x y}$

Simplify each term.

Rewrite $9 x y$ as $3^{2} (x y)$ .

Rewrite $9$ as $3^{2}$ .

$3 \sqrt{x y} - \sqrt{3^{2} x y}$

Add parentheses.

$3 \sqrt{x y} - \sqrt{3^{2} (x y)}$

Pull terms out from under the radical.

$3 \sqrt{x y} - (3 \sqrt{x y})$

Multiply $3$ by $- 1$ .

$3 \sqrt{x y} - 3 \sqrt{x y}$

Subtract $3 \sqrt{x y}$ from $3 \sqrt{x y}$ .

$0$