Answer
$$-5\left(x+2y\right)$$
Work Step by Step
Recall, to simplify rational expressions, we look for common factors in the numerator and the denominator. Doing this, we find:
$$ \frac{5x^2-20y^2}{2y-x}\\ \frac{5\left(x+2y\right)\left(x-2y\right)}{2y-x}\\ -5\left(x+2y\right)$$
