第12页 - 启东中学作业本七年级数学人教版

$\frac {1}{50}$

解：原式$=-\frac {99}{100}×(-\frac {98}{99})×(-\frac {97}{98})×···×(-\frac {1}{2})$

$=-\frac {1}{100}$

$\frac {1}{n}-\frac {1}{n十1}$

$\frac {2022}{2023}$

$\frac {n}{n+1} $

解：原式$=\frac {1}{2}×(\frac {1}{2}-\frac {1}{4}+\frac {1}{4}-\frac {1}{6}+\frac {1}{6}-\frac {1}{8}+···+\frac {1}{2022}- \frac {1}{2024}) $

$=\frac {1}{2}×(\frac {1}{2}-\frac {1}{2024}) $

$=\frac {1}{2}×\frac {1012-1}{2024} $

$=\frac {1011}{4048}$