发布网友 发布时间:2023-07-31 13:05
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热心网友 时间:2024-12-04 18:12
有点麻烦,尽力而为了,(1)原式=1*2+1+2*3+2+3*4+3+……97*98+97+98*99+98 =1*2+2*3+3*4+……+97*98+98*99+(1+2+3+……+98) =1*2*3/3 +2*3*3/3 +3*4*3/3 +……97*98*3/3+98*99*3/3+4851 =2*3*4/3+3*4*3/3+……97*98*3/3+98*99*3/3+4851 =3*4*5/3+……97*98*3/3+98*99*3/3+4851 =98*99*100/3 +4851 =323400+4851 =328251(2)1/1+1/2+1/3+……1/10=7381/2520≈2.9289682539682539682539682539683……可见928之后6位一循环,可推得所求为5(3)原式=(1/1+1/3-2*1/2)/2+(1/2+1/4-2*1/3)/2+……+(1/10+1/12-2*1/11)/2 =0.5*[(1/1+1/2+1/3+……1/10)+(1/3+1/4+……1/12)-2(1/2+1/3+1/4+……1/11)] =0.5*(1-1/2-1/11+1/12) =65/264