7. Given $\frac{1}{1-2^{x}}+\frac{1}{1-2^{y+1}}=1, x+y=$

 untranslated part: 

将上面的文本翻译成英文，请保留源文本的换行和格式，直接输出翻译结果。

 translated part:

7. Given $\frac{1}{1-2^{x}}+\frac{1}{1-2^{y+1}}=1, x+y=$
7. -1 .

Let $f(t)=\frac{1}{2}+\frac{1}{2^{t}-1}$ be an odd function, the original equation can be transformed into $\frac{1}{2}+\frac{1}{2^{x}-1}+\frac{1}{2}+\frac{1}{2^{y+1}-1}=0$, which is $f(x)+f(y+1)=0, f(x)=f(-y-1)$. Since $f(t)$ is monotonically decreasing, we have $x=-y-1$.