已知a=1,b=2,试求:1/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+.1/(a+2009)(b+2009)的值.
问题描述:
已知a=1,b=2,试求:1/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+.1/(a+2009)(b+2009)的值.
答
1/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+.1/(a+2009)(b+2009)
=1/(1×2)+1/(2×3)+.1/(2010×2011)
=1-1/2+1/2-1/3+1/3-1/4+.+1/2010-1/2011
=1-1/2011
=2010/2011