#### Answer

$6x^3y^2\sqrt {xy}$

#### Work Step by Step

$\sqrt {4x^7y^5}+9x^2\sqrt {x^3y^5}-5xy\sqrt {x^5y^3}$ Factor.
$\sqrt {4x^6y^4}\sqrt {xy}+9x^2\sqrt {x^2y^4}\sqrt {xy}-5xy\sqrt {x^4y^2}\sqrt {xy}$ Simplify.
$2x^3y^2\sqrt {xy}+9x^3y^2\sqrt {xy}-5x^3y^2\sqrt {xy}$ Combine like radicals.
$6x^3y^2\sqrt {xy}$