(ab-3/2b-1/2)-(ab-3/2a+1)化简后是多少?当a等于1时,b等于2是,求值

题目=(ab-ab)+3/2(a-b)-(1/2+1)=3/2(a-b)-3/2=3/2(a-b-1)
当a=1,b=2,带入上式=3/2(1-2-1)=-3

3/2(a-b-1), 值为-3

(ab-3/2b-1/2)-(ab-3/2a+1)=ab-3/2b-1/2-ab+3/2a-1=3/2(a-b-1)
当a等于1时,b等于2时,原式＝3/2（1-2-1）=-3