a+b=0 cd=1 x=3或-3a+b-cdx+x/3=0-x+x/3=2x/3=2或-2
2.已知丨2-b丨与丨a-b+4丨互为相反数，则丨2-b丨+丨a-b+4丨=0∴2-b=0, a-b+4=0∴b=2, a=-2∴ab-2007=(-2)×2-2007=-4-2007=-2011
