m=2,n=1.1/mn+1/(m+1)(n+1)+1/(m+2)(n+2)+.+1/(m+10)(n+10)=?
问题描述:
m=2,n=1.1/mn+1/(m+1)(n+1)+1/(m+2)(n+2)+.+1/(m+10)(n+10)=?
答
1/mn+1/(m+1)(n+1)+1/(m+2)(n+2)+.+1/(m+10)(n+10)
=1/1*2+1/2*3+...+1/11*12
=1-1/2+1/2-1/3+..+1/11-1/12
=1-1/12
=11/12