1/1x3+1/3x5+1/5x7+1/7x9+1/9x11+1/11x13=
1个回答
1/1x3 = (1-1/3)/2
1/3x5 = (1/3-1/5)/2
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1/11x13 = (1/11-1/13)/2
以上各式累加
原式=(1-1/13)/2=6/13
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1/5x7+1/7x9+1/9x11+1/11x13+…+1/23x25
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