看啥呢
幼苗
共回答了13个问题采纳率:76.9% 举报
列项
原式=1-5/6+7/12-9/20+!1/30-13/42+15/56-17/72+19/90
=1-﹙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﹚
=1-1/2-1/3+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
=1-1/2+1/10
=1/2+1/10
=3/5
1年前
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