至尊便便
幼苗
共回答了15个问题采纳率:80% 举报
2013÷2013又2013/2014+1/2015
=2013÷2013÷(2013÷2013+2013/2014÷2013)+1/2015
=1÷(1+1/2014)+1/2015
=2014/2015+1/2015
=1
1/5*6*7+1/6*7*8+1/7*8*9
=1/2*(1/5*6-1/6*7+1/6*7-1/7*8+1/7*8-1/8*9)
=1/2*(1/5*6-1/8*9)
=1/2*(1/30-1/72)
=1/2*7/360
=7/720
1年前
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