计算:1/1·5+1/3·7+1/5·9+···+1/21·25
问题描述:
计算:1/1·5+1/3·7+1/5·9+···+1/21·25
答
=1/1-1/5+1/3-1/7+1/5-1/9+……1/21-1/25
=(1+1/3-1/23-1/25)/4
=539/1725
注1/(1*5)=(1/1-1/5)/4
1/(3*7)=(1/3-1/7)/4