作业帮这道题怎么做求简便计算
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这道题怎么做求简便计算
这道题怎么做求简便计算
这道题怎么做求简便计算
( 1+1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)
=[1+(1/2+1/3+1/4)]×(1/2+1/3+1/4+1/5)-[1+(1/2+1/3+1/4+1/5)]×(1/2+1/3+1/4)
=[1×(1/2+1/3+1/4+1/5)+(1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)]-
[1×(1/2+1/3+1/4)+(1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)]
=(1/2+1/3+1/4+1/5)+(1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)-(1/2+1/3+1/4)-(1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)
=(1/2+1/3+1/4+1/5)-(1/2+1/3+1/4)+(1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)-
(1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)
=1/5+0
=1/5