丨ab-2丨+丨1-b丨=0
所以ab-2=1-b=0
ab=2,b=1
则a=2
所以原式=1/1×2+1/2×3+……+1/2011×2012
=1-1/2+1/2-1/3+……+1/2011-1/2012
=1-1/2012
=2011/2012
丨ab-2丨+丨1-b丨=0
所以ab-2=1-b=0
ab=2,b=1
则a=2
所以原式=1/1×2+1/2×3+……+1/2011×2012
=1-1/2+1/2-1/3+……+1/2011-1/2012
=1-1/2012
=2011/2012