1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+1/110 用简便 急
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![1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+1/110 用简便 急](/uploads/image/z/37415-47-5.jpg?t=1%2F2%2B1%2F6%2B1%2F12%2B1%2F20%2B1%2F30%2B1%2F42%2B1%2F56%2B1%2F72%2B1%2F90%2B1%2F110+%E7%94%A8%E7%AE%80%E4%BE%BF+%E6%80%A5)
xŐ1
@Eb=l6&Q!*(bA{B,D^&$XyXha7H+UG3/>35yOkR.ϗJn_Pq2|O5 '♀
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+1/110 用简便 急
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+1/110 用简便 急
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+1/110 用简便 急
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+1/110
=1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+1/7*8+1/8*9+1/9*10+1/10*11
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11
=1-1/11
=10/11
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+1/110
=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)_1/(5*6)+1/(6*7)+1/(7*8)+1/(8*9)+1/(9*10)+1/(10*11)
=1-1/2+1/2-1/3+1/3-1/4...+1/9-1/10+1/10-1/11
=1-1/11
=10/11中间的都笑掉了