\(\frac{4^x}{2^{x+y}}=8\)
\(\frac{2^{2x}}{2^x.2^y}=8\)
\(\frac{2^x}{2^y}=8\)
\(2^x=2^3.2^y\)
\(2^x=2^{3+y}\)
\(\Rightarrow x=3+y\)
\(\frac{9^{x+y}}{3^{5y}}=243\)
\(\frac{3^{2x+2y}}{3^{5y}}=3^5\)
\(\frac{3^{2x}.3^{2y}}{3^{5y}}=3^5\)
\(\frac{3^{2x}}{3^{3y}}=3^5\)
\(3^{2x}=3^5.3^{3y}\)
\(3^{2x}=3^{5+3y}\)
\(\Rightarrow2x=3y+5\)
\(\hept{\begin{cases}2x-3y=5\\x=3+y\end{cases}}\Leftrightarrow\hept{\begin{cases}2\left(3+y\right)-3y=5\\x=3+y\end{cases}}\)
\(\Leftrightarrow\hept{\begin{cases}6+2y-3y=5\\x=3+y\end{cases}}\Leftrightarrow\hept{\begin{cases}-y=-1\\x=3+y\end{cases}}\)
\(\Leftrightarrow\hept{\begin{cases}y=1\\x=4\end{cases}}\)
vậy...
\(\frac{4^x}{2^{x+y}}=8\Leftrightarrow2^{2x}=2^{x+y+3}\Leftrightarrow x=y+3\)
\(9^{x+y}=243.3^{5y}\Leftrightarrow3^{2x+2y}=3^{5y+5}\Leftrightarrow2x=3y+5\)
\(\left(x,y\right)=\left(-1;2\right)\)
