解(a-3)x²y^|a|+(b+2)是五次单项式∴2+|a|=5且b+2=0∴a=3或a=-3∵系数a-3≠0∴a≠3∴a=-3，b=-2∴a²-3ab+b²=9-3×(-3)(-2)+4=13-18=-5
