互为相反数的两个数相加等于0 |a-3|+(2b+1)²=0 因为|a-3|≥0,(2b+1)²≥0 所以|a-3|=0,(2b+1)=0 a-3=0,2b+1=0 a=3,b=-1/2 (b-1)[(2/3)-a] =[(-1/2)-1]×[(2/3)-3] =(-3/2)×(-7/3) =7/2