1/1×2×3×4+1/2×3×4×5+1/3×4×5×6+……+1/17×18×19×201/(1×2×3×4)+1/(2×3×4×5)+1/(3×4×5×6)+……+1/(17×18×19×20)

来源：学生作业帮助网 编辑：作业帮 时间：2024/11/25 22:55:03
1/1×2×3×4+1/2×3×4×5+1/3×4×5×6+……+1/17×18×19×201/(1×2×3×4)+1/(2×3×4×5)+1/(3×4×5×6)+……+1/(17×18×19×20)
xP 0]ǹ(2gdE%4Pct)uVr0P {w =KvtV9[,cl$F6xC[g[i<,AHE8'If{H5rfܦVXC%zHQ}4RM%qG<-[<҆s`VIJ/+#f>س

1/1×2×3×4+1/2×3×4×5+1/3×4×5×6+……+1/17×18×19×201/(1×2×3×4)+1/(2×3×4×5)+1/(3×4×5×6)+……+1/(17×18×19×20)
1/1×2×3×4+1/2×3×4×5+1/3×4×5×6+……+1/17×18×19×20
1/(1×2×3×4)+1/(2×3×4×5)+1/(3×4×5×6)+……+1/(17×18×19×20)

1/1×2×3×4+1/2×3×4×5+1/3×4×5×6+……+1/17×18×19×201/(1×2×3×4)+1/(2×3×4×5)+1/(3×4×5×6)+……+1/(17×18×19×20)
原式=1/3*(1/1*2*3-1/2*3*4+1/2*3*4-1/3*4*5+1/3*4*5-1/4*5*6+1/5*6*7-……+1/17*18*19-1/18*19*20)
=1/3*（1/1*2*3-1/18*19*20）
=1/3*1139/18*19*20
=1139/29754

1 2 3 4 5 1 2 1+1+2+2+3+4+5 1+1 2+2 3+3 4+4 5+5 1,2,3,4,5 1,2,3,4,5, 1 2 3 4 5 1,2,3,4,5 1,2,3,4,5, 1 2 3 4 5 1,2,3,4,5, .1,2,3,4,5, 1,2,3,4,5, 1,2,3,4,5, 1 2 3 4 5 1、2、3、4、5 1,2,3,4,5, 3,4,5,1,2 1、2、3、4、5