punkslh
花朵
共回答了15个问题采纳率:93.3% 举报
念初灬采菊东篱,
因为丨a-2丨+(1-b)=0,所以a=2,b=1
1/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+···+1/(a+2005)(b+2005)
=1/1×2+1/2×3+1/3×4+...+1/2006×1/2007
=1-1/2+1/2-1/3+1/3-1/4+...+1/2006-1/2007
=1-1/2007
=2006/2007
1年前
追问
3
foely
举报
1-1/2+1/2-1/3+1/3-1/4+...+1/2006-1/2007 你怎么算出1-1/2007的
举报
punkslh
1/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+···+1/(a+2005)(b+2005) =1/1×2+1/2×3+1/3×4+...+1/2006×1/2007 =1-1/2+1/2-1/3+1/3-1/4+...+1/2006-1/2007 =1+(-1/2+1/2)+(-1/3+1/3)+(-1/4+1/4)+...+(-1/2006+1/206)-1/2007 =1-1/2007 =2006/2007