a: \(=\dfrac{\sqrt{x}\left(\sqrt{x}-1\right)}{\sqrt{x}-1}=\sqrt{x}\)
b: \(=\dfrac{x\left(\sqrt{x}-2\right)}{-\left(\sqrt{x}-2\right)}=-x\)
c: \(=\dfrac{\sqrt{xy}\left(\sqrt{x}-\sqrt{y}\right)}{\sqrt{x}-\sqrt{y}}=\sqrt{xy}\)
d: \(=\dfrac{\sqrt{ab}\left(\sqrt{a}-\sqrt{b}\right)}{\sqrt{b}\left(\sqrt{b}-\sqrt{a}\right)}=-\sqrt{a}\)
