Question

Rút gọn biểu thức

(3 - căn x)/ (x-9) với x>=0; x#9

Answer 1

\(A=\dfrac{3-\sqrt{x}}{x-9}\)

\(\left\{{}\begin{matrix}x\ne9\\x\ge0\\A=\dfrac{3-\sqrt{x}}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}=\dfrac{-1}{\sqrt{x}+3}\end{matrix}\right.\)

Answer 2

\(\Leftrightarrow\left\{{}\begin{matrix}x\ge0\\\dfrac{3-\sqrt{x}}{x-9}\end{matrix}\right.\)\(\Leftrightarrow\left\{{}\begin{matrix}x\ge0\\\dfrac{3-\sqrt{x}}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}\end{matrix}\right.\Leftrightarrow\)\(\left\{{}\begin{matrix}x\ne3\\x\ge0\\-\dfrac{1}{\sqrt{x}+3}\end{matrix}\right.\)