Question 21Given $x\gt0,$ $y\gt0,$ $x\gt y,$ and $z\ne0.$ The inequality which is not always correct is:$x+z\gt y+z$$x-z\gt y-z$$xz\gt yz$$\dfrac{x}{z^2}\gt\dfrac{y}{z^2}$$xz^2\gt yz^2$