Answer: (e) 0
Solution:
$\begin{array}{l}
\because 2^{x+y}=2^{x-y}=\sqrt{8} \\
\therefore \mathrm{x}+\mathrm{y}=\mathrm{x}-\mathrm{y} \\
\Rightarrow \mathrm{y}=0
\end{array}$
Answer: (e) 0
Solution:
$\begin{array}{l}
\because 2^{x+y}=2^{x-y}=\sqrt{8} \\
\therefore \mathrm{x}+\mathrm{y}=\mathrm{x}-\mathrm{y} \\
\Rightarrow \mathrm{y}=0
\end{array}$