Correct. Write the radical as the quotient of two radicals and then rationalize the denominator.

$\displaystyle\sqrt{{\frac{{{45}{x}}}{{{5}{y}}}}}=\frac{\sqrt{{{45}{x}}}}{\sqrt{{{5}{y}}}}\cdot\frac{\sqrt{{{5}{y}}}}{\sqrt{{{5}{y}}}}=\frac{\sqrt{{{225}{x}{y}}}}{\sqrt{{{{\left({5}{y}\right)}}^{{2}}}}}=\frac{{{15}\sqrt{{{x}{y}}}}}{{{5}{y}}}=\frac{{{3}\sqrt{{{x}{y}}}}}{{y}}\usepackage{cmbright}\Huge\$