cái 15 bé ghi nhầm nhé mn 15 lớn thôi
ĐK: \(\hept{\begin{cases}4x+20\ge0\\x+5\ge0\\16x+80\ge0\end{cases}\Rightarrow x\ge-5}\)
\(\Leftrightarrow\sqrt{4\left(x+5\right)}-3\sqrt{x+5}+\sqrt{16\left(x+5\right)}=15\)
\(\Leftrightarrow2\sqrt{x+5}-3\sqrt{x+5}+4\sqrt{x+5}=15\)
\(\Leftrightarrow3\sqrt{x+5}=15\Leftrightarrow\sqrt{x+5}=5\Leftrightarrow x+5=5^2=25\Leftrightarrow x=20\)