已知:根号a-1+(ab-2)²=0求:1/(a+1)(b+1)+1/(a+2)(b+2)+……+1/(a+2007)(b+2007)+1/(a+2008)(b+2008).

来源:学生作业帮助网 编辑:作业帮 时间:2024/11/16 21:32:27

已知:根号a-1+(ab-2)²=0求:1/(a+1)(b+1)+1/(a+2)(b+2)+……+1/(a+2007)(b+2007)+1/(a+2008)(b+2008).
已知:根号a-1+(ab-2)²=0
求:1/(a+1)(b+1)+1/(a+2)(b+2)+……+1/(a+2007)(b+2007)+1/(a+2008)(b+2008).

已知:根号a-1+(ab-2)²=0求:1/(a+1)(b+1)+1/(a+2)(b+2)+……+1/(a+2007)(b+2007)+1/(a+2008)(b+2008).
根号a-1+(ab-2)²=0
所以有a-1=0且ab-2=0
得到a=1,b=2
那么,1/(a+1)(b+1)+1/(a+2)(b+2)+……+1/(a+2007)(b+2007)+1/(a+2008)(b+2008)=1/2*3+1/3*4+.+1/2009*2010
=1/2-1/3+1/3-1/4+.+1/2009-1/2010
=1/2-1/2010
=502/1005

a-1=0
ab-2=0
∴a=1
b=2
1/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+……+1/(a+2007)(b+2007)+1/(a+2008)(b+2008).
=1/1*2+1/2*3+1/3*4+……+1/2009*2010
=1-1/2+1/2-1/3+1/3-1/4+1/4-……-1/2009+1/2009-1/2010
=1-1/2010
=2009/2010
=502/1005