有两个非负数和为0得ab-2=0,b-1=0,所以a=2,b=1
结果就成了1/(1*2)+1/(2*3)+1/(3*4)+……+1/(2011*2012)
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+……+(1/2011-1/2012)=1-1/2012=2011/2012
有两个非负数和为0得ab-2=0,b-1=0,所以a=2,b=1
结果就成了1/(1*2)+1/(2*3)+1/(3*4)+……+1/(2011*2012)
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+……+(1/2011-1/2012)=1-1/2012=2011/2012