1/6+1/24+1/60+1/120+1/210+1/336=?

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1/6+1/24+1/60+1/120+1/210+1/336=?

1/6+1/24+1/60+1/120+1/210+1/336=?
1/6+1/24+1/60+1/120+1/210+1/336=?

1/6+1/24+1/60+1/120+1/210+1/336=?
使用列项相消法
6*7*8=336
5*6*7=210
4*5*6=120
3*4*5=60
2*3*4=24
1*2*3=6
1/(1*2*3)=(1/(1*2)-1/(2*3))/2
1/(2*3*4)=(1/(2*3)-1/(3*4))/2
……
原式=(1/(1*2)-1/(7*8))/2=(1/2-1/56)/2=7/112

1/6+1/24+1/60+1/120+1/210+1/336+1/112 =(2/6+2/24+2/60+2/120+2/210+2/336+2/112)*1/2 =(1/1*2-1/2*3+1/2*3-1/3*4