作业帮1/5+1/45+1/117+1/221+1/357简算
来源：学生作业帮助网 编辑：作业帮 时间：2024/05/06 10:49:33
1/5+1/45+1/117+1/221+1/357简算
1/5+1/45+1/117+1/221+1/357简算
1/5+1/45+1/117+1/221+1/357简算
原式=1/(1x5）+1/(5x9)+1/(9x13)+1/(13x17)+1/(17x21)
=1/4x(1-1/5+1/5-1/9+1/9-1/13+1/13-1/17+1/17-1/21)
=1/4x20/21
=5/21