巧算:2/1-6/1-12/1-20/1-30/1-42/1-56/1-72/1

来源:学生作业帮助网 编辑:作业帮 时间:2024/10/02 09:19:18
巧算:2/1-6/1-12/1-20/1-30/1-42/1-56/1-72/1
x){}ueokĆ 0& )HȲI*'U~ Yi!ad$A k 0, 4HTiG ˀ34PPx%Ov>yc =l[=  @~s'fY

巧算:2/1-6/1-12/1-20/1-30/1-42/1-56/1-72/1
巧算:2/1-6/1-12/1-20/1-30/1-42/1-56/1-72/1

巧算:2/1-6/1-12/1-20/1-30/1-42/1-56/1-72/1
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90
=1-1/2+1/2-1/3+1/3-1/4+……1/9-1/10 (除了1与1/10,两两抵消)
=1-1/10
=9/10