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1/20加1/30加1/42加1/56加1/72简便计算,求.
题目详情
1/20加1/30加1/42加1/56加1/72
简便计算,求.
简便计算,求.
▼优质解答
答案和解析
=1/4*5+1/5*6+1/6*7+1/7*8+1/8*9
=1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1/4-1/9
=5/36
=1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1/4-1/9
=5/36
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