\(4,ĐK:x\ge-5\\ PT\Leftrightarrow2\sqrt{x+5}-2\sqrt{x+5}+3\sqrt{x+5}=6\\ \Leftrightarrow\sqrt{x+5}=2\\ \Leftrightarrow x+5=4\Leftrightarrow x=-1\left(tm\right)\)
\(5,\\ a,A=\dfrac{1-\sqrt{x}}{\sqrt{x}\left(\sqrt{x}+2\right)}\cdot\dfrac{\left(\sqrt{x}+2\right)^2}{1-\sqrt{x}}=\dfrac{\sqrt{x}+2}{\sqrt{x}}\\ b,A=\dfrac{5}{2}\Leftrightarrow5\sqrt{x}=2\sqrt{x}+4\\ \Leftrightarrow3\sqrt{x}=4\Leftrightarrow\sqrt{x}=\dfrac{4}{3}\Leftrightarrow x=\dfrac{16}{9}\left(tm\right)\)
Bài 4:
Ta có: \(\sqrt{4x+20}-2\sqrt{x+5}+\sqrt{9x+45}=6\)
\(\Leftrightarrow3\sqrt{x+5}=6\)
\(\Leftrightarrow x+5=4\)
hay x=-1
