a=-2,b=-1,则1/ab+1/(a+1)(a+1)+.+1/(a+2006)(a+2006)=?

问题输入有错误吧,不然谁有本事将值求出呀.
(1)a=-2时,1/(a+2)都没有意义,怎么计算
(2)下面b没有了,怎么回事?
自认为a=2,b=1才可以
1/(ab)+1/[(a+1)(b+1)]+1/[(a+2)(b+2)]+.+1/[(a+2006)(b+2006)]
=1/2+1/(2*3)+1/(3*4)+.+1/(2007*208)
=1/2+1/2-1/3+1/3-1/4+.+1/2007-1/2008
=1-1/2008
=2007/2008