summerghost
幼苗
共回答了23个问题采纳率:91.3% 举报
1 11x13x10x(3/11-1/13)-120 =11x13x10x3/11-11x13x10x1/13-120=390-110-120=160.
2 (2890+5/6+7/8+7/10)/(5/6+7/8+7/10)=2890/(5/6+7/8+7/10)+1=2890/[(5*20+7*15+7*12)/120+1=1200+1`=1201
3 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)+(1/4-1/5+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)+(1/8-1/9)+(1/9-1/10)=1-1/10=9/10
1年前
追问
7
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summerghost
(2890+5/6+7/8+7/10)/(5/6+7/8+7/10)= [2890+(5/6+7/8+7/10))/(5/6+7/8+7/10)=2890/(5/6+7/8+7/10)+1=[2890/(289/120)]+1=1200+1=1201