Rút gọn
A=\(\left(\dfrac{\sqrt{x}}{\sqrt{x}-2}+\dfrac{1}{\sqrt{x}+2}+\dfrac{6-7\sqrt{x}}{x-4}\right)\left(\sqrt{x}-2\right)\)
B=\(\left(1+\dfrac{x+\sqrt{x}}{\sqrt{x}+1}\right)\left(1+\dfrac{x-\sqrt{x}}{1-\sqrt{x}}\right)\)
C=\(\left(\dfrac{1}{x-4}-\dfrac{1}{x+4\sqrt{x}+4}\right)\dfrac{x+2\sqrt{x}}{\sqrt{x}}\)
a: \(=\dfrac{x+2\sqrt{x}+\sqrt{x}-2+6-7\sqrt{x}}{x-4}\cdot\left(\sqrt{x}-2\right)\)
\(=\dfrac{x-4\sqrt{x}+4}{\sqrt{x}+2}\)
b: \(=\left(1+\sqrt{x}\right)\cdot\left(1-\sqrt{x}\right)=1-x\)
c: \(=\dfrac{\sqrt{x}+2-\sqrt{x}+2}{\left(\sqrt{x}+2\right)^2\cdot\left(\sqrt{x}-2\right)}\cdot\dfrac{\sqrt{x}\left(\sqrt{x}+2\right)}{\sqrt{x}}\)
\(=\dfrac{2\sqrt{x}}{x-4}\)
