Question

frac{x^{2}-6xsqrt{y}+9y}{3sqrt{y}-x}

Answer 1

$frac{x^{2}-6xsqrt{y}+9y}{3sqrt{y}-x}=frac{(x-3sqrt y)^2}{3sqrt y-x}=-frac{(x-3sqrt y)^2}{x-3sqrt y}=-(x-3sqrt y)=3sqrt y-x$