第1个回答 2011-09-11
1又1/2+2又1/6+3又1/12+4又1/20+5又1/30+6又1/42
=1+1/2+2+1/6+3+1/12+4+1/20+5+1/30+6+1/42
=(1+2+3+4+5+6)+(1/2+1/6+1/12+1/20+1/30+1/42)
=21+(1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7)
=21+(1-1/7)
=21+6/7
=21又6/7本回答被提问者采纳
=1+1/2+2+1/6+3+1/12+4+1/20+5+1/30+6+1/42
=(1+2+3+4+5+6)+(1/2+1/6+1/12+1/20+1/30+1/42)
=21+(1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7)
=21+(1-1/7)
=21+6/7
=21又6/7本回答被提问者采纳
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