a) \(\Leftrightarrow2^{x+1}.3^y=2^{2x}.3^x\)\(\Leftrightarrow\hept{\begin{cases}x+1=2x\\y=x\end{cases}\Leftrightarrow\hept{\begin{cases}x=1\\y=x=1\end{cases}}}\)
b) \(\Leftrightarrow2^x.5^{x-y}=2^{2y}.5^y\Leftrightarrow\hept{\begin{cases}x=2y\\x-y=y\end{cases}\Leftrightarrow x=2y}\)
c) \(2^x=4^{y-1}\Leftrightarrow2^x=2^{2y-2}\Leftrightarrow x=2y-2\)
\(27^y=3^{x+8}\Leftrightarrow3^{3y}=3^{x+8}\Leftrightarrow3y=x+8\)
\(\Rightarrow\hept{\begin{cases}x=10\\y=6\end{cases}}\)