bài 14:
a: \(A=\dfrac{x\sqrt{x}-1}{x-\sqrt{x}}-\dfrac{x\sqrt{x}+1}{x+\sqrt{x}}+\dfrac{x+1}{\sqrt{x}}\)
\(=\dfrac{\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}{\sqrt{x}\cdot\left(\sqrt{x}-1\right)}-\dfrac{\left(\sqrt{x}+1\right)\left(x-\sqrt{x}+1\right)}{\sqrt{x}\left(\sqrt{x}+1\right)}+\dfrac{x+1}{\sqrt{x}}\)
\(=\dfrac{x+\sqrt{x}+1-x+\sqrt{x}-1+x+1}{\sqrt{x}}=\dfrac{x+2\sqrt{x}+1}{\sqrt{x}}\)
b: \(A=\dfrac{9}{2}\)
=>\(2\left(x+2\sqrt{x}+1\right)=9\sqrt{x}\)
=>\(2x-5\sqrt{x}+2=0\)
=>\(\left(\sqrt{x}-2\right)\left(2\sqrt{x}-1\right)=0\)
=>\(\left[{}\begin{matrix}x=4\left(nhận\right)\\x=\dfrac{1}{4}\left(nhận\right)\end{matrix}\right.\)
