Bài 10:
a: \(A=\dfrac{a-\sqrt{a}-a-\sqrt{a}+1}{a-1}\cdot\dfrac{2\left(\sqrt{a}+1\right)}{a}\)
\(=\dfrac{-2\sqrt{a}+1}{a-1}\cdot\dfrac{2\left(\sqrt{a}+1\right)}{a}\)
\(=\dfrac{-4\sqrt{a}+2}{\left(\sqrt{a}-1\right)\cdot a}\)
b: Thay a=25 vào A, ta được:
\(A=\dfrac{-4\cdot5+2}{\left(5-1\right)\cdot25}=\dfrac{-6}{4\cdot25}=-0.06\)