\(A=\left(\dfrac{1}{\sqrt{a}}+\dfrac{1}{1-\sqrt{a}}\right).\dfrac{\sqrt{a}-a}{\sqrt{a}-2}\\ =\left(\dfrac{1-\sqrt{a}}{\sqrt{a}\left(1-\sqrt{a}\right)}+\dfrac{\sqrt{a}}{\sqrt{a}\left(1-\sqrt{a}\right)}\right).\dfrac{\sqrt{a}\left(1-\sqrt{a}\right)}{\sqrt{a}-2}\\ =\dfrac{1-\sqrt{a}+\sqrt{a}}{\sqrt{a}\left(1-\sqrt{a}\right)}.\dfrac{\sqrt{a}\left(1-\sqrt{a}\right)}{\sqrt{a}-2}\\ =\dfrac{1}{\sqrt{a}-2}\\ B=\left(\dfrac{\sqrt{x}}{2}-\dfrac{1}{2\sqrt{x}}\right).\dfrac{4x}{x-1}\\ =\left(\dfrac{\sqrt{x}.\sqrt{x}}{2\sqrt{x}}-\dfrac{1}{2\sqrt{x}}\right).\dfrac{4x}{x-1}\\ =\dfrac{x-1}{2\sqrt{x}}.\dfrac{4x}{x-1}\\ =2\sqrt{x}\)
\(A=\left(\dfrac{1}{\sqrt{a}}+\dfrac{1}{1-\sqrt{a}}\right)\cdot\dfrac{\sqrt{a}-a}{\sqrt{a}-2}\) ĐK: \(a>0;a\notin\left\{1;4\right\}\)
\(A=\left(\dfrac{1-\sqrt{a}}{\sqrt{a}\left(1-\sqrt{a}\right)}+\dfrac{\sqrt{a}}{\sqrt{a}\left(1-\sqrt{a}\right)}\right)\cdot\dfrac{\sqrt{a}\left(1-\sqrt{a}\right)}{\sqrt{a}-2}\)
\(A=\dfrac{1}{\sqrt{a}\left(1-\sqrt{a}\right)}\cdot\dfrac{\sqrt{a}\left(1-\sqrt{a}\right)}{\sqrt{a}-2}\)
\(A=\dfrac{1}{\sqrt{a}-2}\)
\(B=\left(\dfrac{\sqrt{x}}{2}-\dfrac{1}{2\sqrt{x}}\right)\cdot\dfrac{4x}{x-1}\) ĐK: \(x>0;x\notin\left\{1\right\}\)
\(B=\left(\dfrac{x}{2\sqrt{x}}-\dfrac{1}{2\sqrt{x}}\right)\cdot\dfrac{4x}{x-1}\)
\(B=\dfrac{x-1}{2\sqrt{x}}\cdot\dfrac{4x}{x-1}\)
\(B=\dfrac{4x}{2\sqrt{x}}\)
\(B=2\sqrt{x}\)
