[3a-2]的平方+2a-b-3的绝对值等于零
得3a-2=0,2a-b-3=0
a=2/3,b=-5/3
5[2a-b]-2[6a-2b+2｝+｛4a-3b-1/2｝
=2a-4b-4.5
=4/3+20/3-4.5
=8-4.5=3.5