If \(\ 2^x+2^y=2^{x+y} \), then \(\ \frac{d y}{d x}= \)

\(\ 2^{x-y} \frac{2^y-1}{2^x-1} \)

\(\ 2^{x-y}\left(\frac{2^y-1}{1-2^x}\right) \)

\(\ \frac{2^x+2^y}{2^x-2^y} \)

None of these