c: \(C=\dfrac{\left(\sqrt{a}-2\right)\left(a+2\sqrt{a}+4\right)+2\sqrt{a}\left(\sqrt{a}-2\right)}{\left(\sqrt{a}-2\right)\left(\sqrt{a}+2\right)}\)
\(=\dfrac{a+2\sqrt{a}+4+2\sqrt{a}}{\sqrt{a}+2}=\sqrt{a}+2\)
d: \(=\dfrac{1}{2a-1}\cdot a^2\sqrt{5}\cdot\left|2a-1\right|=\pm a^2\sqrt{5}\)
e: \(=\dfrac{2}{\left(x-y\right)\left(x+y\right)}\cdot\dfrac{\sqrt{3}\left|x+y\right|}{2}\)
\(=\pm\dfrac{\sqrt{3}}{x-y}\)