Bài 4:
Ta có: \(P=\left(\dfrac{1}{\sqrt{x}-1}-\dfrac{1}{\sqrt{x}}\right):\left(\dfrac{\sqrt{x}+1}{\sqrt{x}-2}-\dfrac{\sqrt{x}+2}{\sqrt{x}-1}\right)\)
\(=\dfrac{\sqrt{x}-\sqrt{x}+1}{\sqrt{x}\left(\sqrt{x}-1\right)}:\dfrac{x-1-x+4}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-1\right)}\)
\(=\dfrac{\sqrt{x}-2}{3\sqrt{x}}\)
Bài 2:
a: Ta có: \(\sqrt[3]{27}-\sqrt[3]{64}+2\cdot\sqrt[3]{8}\)
\(=3-4+2\cdot2\)
=3
b: Ta có: \(2\sqrt{12}-4\sqrt{27}+\sqrt{48}-\sqrt{75}\)
\(=4\sqrt{3}-12\sqrt{3}+4\sqrt{3}-5\sqrt{3}\)
\(=-9\sqrt{3}\)
c: Ta có: \(3\sqrt{\dfrac{3}{2}}-\sqrt{6}+\sqrt{\dfrac{2}{3}}\)
\(=\dfrac{3}{2}\sqrt{6}-\sqrt{6}+\dfrac{1}{3}\sqrt{6}\)
\(=\dfrac{5}{6}\sqrt{6}\)
