第1个回答 2016-12-30
1/1*3+1/3*5+1/5*7+1/7*9+1/9*11+1/11*13+1/13*15
=1/2*(1-1/3+1/3-1/5+...+1/13-1/15)
=1/2*(1-1/15)
=1/2*14/15
=7/1追答
=1/2*(1-1/3+1/3-1/5+...+1/13-1/15)
=1/2*(1-1/15)
=1/2*14/15
=7/1追答
7/15
第2个回答 2016-12-30
解原式=1/2*(2/3*5+2/5*7+.....+2/13*15)
=1/2(1/3-1/5+1/5-1/7+....+1/13-1/15)
=1/2*(1/3-1/15)
=1/2*(4/15)
=2/15本回答被网友采纳
=1/2(1/3-1/5+1/5-1/7+....+1/13-1/15)
=1/2*(1/3-1/15)
=1/2*(4/15)
=2/15本回答被网友采纳
第3个回答 2016-12-30
第4个回答 2016-12-30
1/3*5+1/5*7+1/7*9+1/9*11+1/11*13+1/13*15
=1/2*(1/3-1/5)+2*(1/5-1/7)+2*(1/7-1/9)+....2*(1/13-1/15)
=1/2*(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13+1/13-1/15)
=1/2*(1/3-1/15)
=1/2*(5/15-1/15)
=1/2*(4/15)
=2/15
=1/2*(1/3-1/5)+2*(1/5-1/7)+2*(1/7-1/9)+....2*(1/13-1/15)
=1/2*(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13+1/13-1/15)
=1/2*(1/3-1/15)
=1/2*(5/15-1/15)
=1/2*(4/15)
=2/15
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