a) \(B=\dfrac{\sqrt{x}\left(3-\sqrt{x}\right)+x+9}{\left(3+\sqrt{x}\right)\left(3-\sqrt{x}\right)}:\dfrac{3\sqrt{x}+1+2\left(\sqrt{x}-3\right)}{\sqrt{x}\left(\sqrt{x}-3\right)}\left(x>0,x\ne3\right)\)
\(B=\dfrac{3\left(\sqrt{x}+3\right)}{\left(3+\sqrt{x}\right)\left(3-\sqrt{x}\right)}\cdot\dfrac{\sqrt{x}\left(\sqrt{x}-3\right)}{5\left(\sqrt{x}-1\right)}\)
\(B=\dfrac{3\sqrt{x}\left(\sqrt{x}-3\right)}{5\left(\sqrt{x}-1\right)\left(3-\sqrt{x}\right)}=-\dfrac{3\sqrt{x}}{5\left(\sqrt{x}-1\right)}\)
b) Để \(B< 0\Leftrightarrow\dfrac{-3\sqrt{x}}{5\left(\sqrt{x}-1\right)}< 0\)
Mà \(-3\sqrt{x}< 0\)
\(\Leftrightarrow5\left(\sqrt{x}-1\right)>0\Leftrightarrow\sqrt{x}-1>0\)
\(\Leftrightarrow\sqrt{x}>1\Leftrightarrow x>1\)
Tick hộ tui nha 😘
