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=1-(2+1)/1×2+(2+3)/2×3-(3+4)/3×4+……-(9+10)/9×10+(10+11)/10×11
=1-1/1-1/2+1/2+1/3-1/3-1/4+1/4-1/9-1/10+1/10+1/11
=1/11
=1-1/1-1/2+1/2+1/3-1/3-1/4+1/4-1/9-1/10+1/10+1/11
=1/11
1年前
4
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