如果有理数a,b满足|ab-2|+(1-a)^2=0,求1/(a+1)(b+2)+1/(a+3)(b+4)+…+1/(a+2009)(b+2010)

问题描述:

如果有理数a,b满足|ab-2|+(1-a)^2=0,求1/(a+1)(b+2)+1/(a+3)(b+4)+…+1/(a+2009)(b+2010)

因为 |ab-2| ≥0,(1-a)^2≥0,而 |ab-2|+(1-a)^2=0 ,所以ab-2=0,1-a=0
所以 a=1,b=2.1/(a+1)(b+2)+1/(a+3)(b+4)+…+1/(a+2009)(b+2010)=1/(1+1)(2+2)+1/(1+3)(2+4)+…+1/(1+2009)(2+2010)=1/2*【(1/2-1/4)+(1/4-1/8)+…+(1/1005-1/1006)】=
1/2*(1/2-1/1006)…… OK了错了,我知道了,应该是=1/2*【(1/2-1/4)+(1/4-1/6)+…+(1/2010-1/2012)】=1/2*(1/2-1/2012)=1/2*1005/2012=1005/4024谢谢因为 |ab-2| ≥0, (1-a)^2≥0,而 |ab-2|+(1-a)^2=0 ,所以ab-2=0,1-a=0所以 a=1,b=2.1/(a+1)(b+2)+1/(a+3)(b+4)+…+1/(a+2009)(b+2010)=1/(1+1)(2+2)+1/(1+3)(2+4)+…+1/(1+2009)(2+2010)=1/2*【(1/2-1/4)+(1/4-1/6)+…+(1/2010-1/2012)】=1/2*(1/2-1/2012)=……