Question

Answer 1

a: ĐKXĐ: x>=0; \(x\notin\left\{4;9\right\}\)

\(A=\dfrac{x-9-x+3\sqrt{x}}{x-9}:\left(\dfrac{-\left(x-9\right)+x-4\sqrt{x}+4-9+x}{\left(\sqrt{x}+3\right)\left(\sqrt{x}-2\right)}\right)\)

\(=\dfrac{3\left(\sqrt{x}-3\right)}{x-9}\cdot\dfrac{\left(\sqrt{x}+3\right)\left(\sqrt{x}-2\right)}{-x+9+2x-4\sqrt{x}-5}\)

\(=\dfrac{3\left(\sqrt{x}-2\right)}{x-4\sqrt{x}+4}=\dfrac{3}{\sqrt{x}-2}\)

b: Để C=4 thì \(\sqrt{x}-2=\dfrac{3}{4}\)

=>x=121/16