Ta có: \(N=\frac{3\sqrt{a}-2a-1}{4a-4\sqrt{a}+1}\)
\(=\frac{-2a+2\sqrt{a}+\sqrt{a}-1}{\left(2\sqrt{a}-1\right)^2}\)
\(=\frac{-2\sqrt{a}\left(\sqrt{a}-1\right)+\left(\sqrt{a}-1\right)}{\left(2\sqrt{a}-1\right)^{^2}}\)
\(=\frac{\left(\sqrt{a}-1\right)\left(1-2\sqrt{a}\right)}{\left(1-2\sqrt{a}\right)^2}=\frac{\sqrt{a}-1}{1-2\sqrt{a}}\)