Question

Answer 1

a: Thay \(x=3-2\sqrt{2}\) vào A, ta được:

\(A=\dfrac{\sqrt{2}-1-2}{\sqrt{2}-1+2}=\dfrac{\sqrt{2}-3}{\sqrt{2}+1}=5-4\sqrt{2}\)

b: Ta có: \(B=\left(\dfrac{1}{\sqrt{x}+2}+\dfrac{1}{\sqrt{x}-2}\right)\cdot\dfrac{\sqrt{x}-2}{2}\)

\(=\dfrac{\sqrt{x}-2+\sqrt{x}+2}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}\cdot\dfrac{\sqrt{x}-2}{2}\)

\(=\dfrac{\sqrt{x}}{\sqrt{x}+2}\)