l 1⼀3-1⼀2 l+l1⼀4-1⼀3l+l1⼀5-1⼀4l+.+l1⼀10-1⼀9l

2024-11-16 10:27:48
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回答(1):

原式=1/2-1/3+1/3-1/4+1/4-1/5.+.+1/9-1/10=1/2+1/10=6/10=3/5