\(a+2b=3\sqrt{ab}\Leftrightarrow\left(\sqrt{a}-\sqrt{b}\right)\left(\sqrt{a}-2\sqrt{b}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}a=b\\a=4b\end{matrix}\right.\)
khi \(a=b\) \(\Rightarrow\dfrac{a}{2b}=\dfrac{a}{2a}=\dfrac{1}{2}\)
khi \(a=4b\)\(\Rightarrow\dfrac{a}{2b}=\dfrac{4b}{2b}=2\)