计算x-1分之1+(x-1)(x-2)分之1+(x-2)(x-3)分之1+...+(x-9)(x-10)分之1
来源:学生作业帮 编辑:灵鹊做题网作业帮 分类:数学作业 时间:2024/05/30 17:13:34
计算x-1分之1+(x-1)(x-2)分之1+(x-2)(x-3)分之1+...+(x-9)(x-10)分之1
思路:我们知道:1/3*2=(3-2)/3*2=3/3*2-2/3*2=1/2-1/3
类比得:1/n*(n-1)=[n-(n-1)]/n*(n-1)=n/n*(n-1)-(n-1)/n*(n-1)=1/(n-1)-1/n
所以1/(x-1)(x-2)=1/(x-2)-1/(x-1),1/(x-9)(x-10)=1/(x-10)-1/(x-9),.
所以1/(x-1)+ 1/(x-1)(x-2)+1/(x-2)(x-3)+.+1/(x-9)(x-10)
=1/(x-1)+ 1/(x-2)-1/(x-1)+1/(x-3)-1/(x-2)+.+ 1/(x-10)-1/(x-9)
=1/(x-10)
类比得:1/n*(n-1)=[n-(n-1)]/n*(n-1)=n/n*(n-1)-(n-1)/n*(n-1)=1/(n-1)-1/n
所以1/(x-1)(x-2)=1/(x-2)-1/(x-1),1/(x-9)(x-10)=1/(x-10)-1/(x-9),.
所以1/(x-1)+ 1/(x-1)(x-2)+1/(x-2)(x-3)+.+1/(x-9)(x-10)
=1/(x-1)+ 1/(x-2)-1/(x-1)+1/(x-3)-1/(x-2)+.+ 1/(x-10)-1/(x-9)
=1/(x-10)
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