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1/3*5+1/5*7+1/7*9+1/9*11+1/11*13+1/13*15=?
题目详情
1/3*5+1/5*7+1/7*9+1/9*11+1/11*13+1/13*15=?
▼优质解答
答案和解析
原式=1/3*5+1/5*7+1/7*9+1/9*11+1/11*13+1/13*15
=1/2(1/3-1/5+1/5-1/7+.+1/11-1/13+1/13-1/15)
=1/2(1/3-1/15)
=1/2 * 4/15
=2/15 .
=1/2(1/3-1/5+1/5-1/7+.+1/11-1/13+1/13-1/15)
=1/2(1/3-1/15)
=1/2 * 4/15
=2/15 .
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