已知.1/n(n+1)=A/n+B/n+1,试求A,B的值,并利用他计算(1)1/1*2+1/2*3+1/3*4+...+1/99*1001/n(n+1)+1/(n+1)*(n+2)+1/(n+2)*(n+3)+...+1/(n+99)*(n+100)
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已知.1/n(n+1)=A/n+B/n+1,试求A,B的值,并利用他计算(1)1/1*2+1/2*3+1/3*4+...+1/99*1001/n(n+1)+1/(n+1)*(n+2)+1/(n+2)*(n+3)+...+1/(n+99)*(n+100)
已知.1/n(n+1)=A/n+B/n+1,试求A,B的值,并利用他计算(1)1/1*2+1/2*3+1/3*4+...+1/99*100
1/n(n+1)+1/(n+1)*(n+2)+1/(n+2)*(n+3)+...+1/(n+99)*(n+100)
已知.1/n(n+1)=A/n+B/n+1,试求A,B的值,并利用他计算(1)1/1*2+1/2*3+1/3*4+...+1/99*1001/n(n+1)+1/(n+1)*(n+2)+1/(n+2)*(n+3)+...+1/(n+99)*(n+100)
提示:1/n(n+1) = ((n+1)-n)/(n*(n+1)) = 1/n-1/(n+1)
故 1/n(n+1)+1/(n+1)*(n+2)+1/(n+2)*(n+3)+...+1/(n+99)*(n+100)的
每一项拆开消项,等于 (1/n-1/(n+1))+(1/(n+1)-1/(n+2))+...+(1/(n+99)-1/(n+100)) = 1/n - 1/(n+100)
= 100/(n+100)
1/n(n+1)=1/n-1/(n+1) 所以A=1, B=-1
因此,计算算式=1/1-1/2+1/2-1/3+1/3-1/4+......+1/98-1/99+1/99-1/100
=1/1+(-1/2+1/2)+(-1/2+1/3)+......+(-1/99+1/99)-1/100=1/1-1/100=99/100