首页 > 留学知识库

问题: 计算

|ab+2|+|a+1|等于0,计算: 1/(a-1)(b+1) + 1/(a-2)(b+2)+......+ 1/(a-2009)(b+2009)

解答:

|ab+2|+|a+1|=0
ab+2=0-------ab=-2
a+1=0---------a=-1,b=2
1/(a-1)(b+1) + 1/(a-2)(b+2)+......+ 1/(a-2009)(b+2009)
=-1/2*3-1/3*4-1/4*5-......-1/2010*2011
=-[(3-2)/2*3+(4-3)/3*4+(5-4)/4*5+......+(2011-2010)/2010*2011]
=-[1/2-1/3+1/3-1/4+1/4-1/5+......+1/2010-1/2011]
=-[1/2-1/2011]
=-2009/4022