1⼀2+1⼀6+1⼀12+1⼀20++1⼀90

2025-02-01 00:01:54
推荐回答(2个)
回答1:

1/2+1/6+1/12+1/20+⋯+1/90
=1-1/2+1/2-1/3+1/3-1/4+……+1/9-1/10
=1-1/10
=9/10

回答2: