解:由题意可得:
丨a-1丨+(ab-2)^2=0
a-1=0,ab-2=0
a=1,b=2
原式=1/2+1/2*3+1/3*4+.......+1/2002*2003
=1-1/2+1/2-1/3+1/3-1/4+....1/2002-1/2003
=1-1/2003
=2002/2003