16．观察下列等式：
$1-\frac{1}{2}=\frac{1}{2}$
$1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}=\frac{1}{3}+\frac{1}{4}$
$1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+\frac{1}{5}-\frac{1}{6}=\frac{1}{4}+\frac{1}{5}+\frac{1}{6}$
据此规律，第 $n$ 个等式可为 $\_\_\_\_$ ．
Answer key
$1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+\cdots+\frac{1}{2 n-1}-\frac{1}{2 n}=\frac{1}{n+1}+\frac{1}{n+2}+\cdots+\frac{1}{2 n}$