\(=\dfrac{y}{x\left(2x-y\right)}+\dfrac{4x}{y\left(y-2x\right)}\)
\(=\dfrac{y^2-4x^2}{xy\left(2x-y\right)}=\dfrac{\left(y-2x\right)\left(y+2x\right)}{xy\left(2x-y\right)}=\dfrac{-y-2x}{xy}\)
\(\dfrac{y}{2x^2-xy}+\dfrac{4x}{y^2-2xy}\\ =\dfrac{y}{x\left(2x-y\right)}+\dfrac{4x}{y\left(y-2x\right)}\\ =\dfrac{y^2\left(y-2x\right)}{xy\left(2x-y\right)\left(y-2x\right)}+\dfrac{4x^2\left(2x-y\right)}{xy\left(2x-y\right)\left(y-2x\right)}\\ =\dfrac{y^2\left(y-2x\right)+4x^2\left(2x-y\right)}{xy\left(2x-y\right)\left(y-2x\right)}\\ =\dfrac{y^2\left(y-2x\right)-4x^2\left(y-2x\right)}{xy\left(2x-y\right)\left(y-2x\right)}\\ =\dfrac{\left(y-2x\right)\left(y^2-4x^2\right)}{xy\left(2x-y\right)\left(y-2x\right)}\\ =\dfrac{\left(y-2x\right)\left(y+2x\right)}{xy\left(2x-y\right)}\\ =\dfrac{-\left(2x-y\right)\left(y+2x\right)}{xy\left(2x-y\right)}\\ =\dfrac{-\left(y+2x\right)}{xy}\)
