Question 4The expression $$ \frac{P+Q}{P-Q}-\frac{P-Q}{P+Q}, $$ where $P=x+y$ and $Q=x-y,$ is equivalent to:$\dfrac{x^2-y^2}{xy}$$\dfrac{x^2-y^2}{2xy}$$1$$\dfrac{x^2+y^2}{xy}$$\dfrac{x^2+y^2}{2xy}$