1. $\frac{1}{1-\log _{2} 20}+\frac{1}{1-\log _{5} 50}$ The value is $\qquad$
$$
\frac{1}{1-\log _{2} 20}+\frac{1}{1-\log _{5} 50}=-\frac{1}{\log _{2} 10}-\frac{1}{\log _{5} 10}=-\lg 2-\lg 5=-1 .
$$

Translate the above text into English, keeping the original text's line breaks and format:

$$
\frac{1}{1-\log _{2} 20}+\frac{1}{1-\log _{5} 50}=-\frac{1}{\log _{2} 10}-\frac{1}{\log _{5} 10}=-\lg 2-\lg 5=-1 .
$$