Bài 2:
a: Ta có: \(E=\dfrac{1}{2\sqrt{a}-2}-\dfrac{1}{2\sqrt{a}+2}+\dfrac{\sqrt{a}}{1-a}\)
\(=\dfrac{\sqrt{a}+1-\sqrt{a}+1-2\sqrt{a}}{2\left(\sqrt{a}+1\right)\left(\sqrt{a}-1\right)}\)
\(=\dfrac{-2\left(\sqrt{a}-1\right)}{2\left(\sqrt{a}+1\right)\left(\sqrt{a}-1\right)}\)
\(=\dfrac{-1}{\sqrt{a}+1}\)
b: Thay \(a=\dfrac{4}{9}\) vào E, ta được:
\(E=-1:\left(\dfrac{2}{3}+1\right)=-1:\dfrac{5}{3}=-\dfrac{3}{5}\)
Đúng 3
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