2(3a平方b-ab平方)-4a平方b+5-3(2/3a平方b-ab2次方+4) =6a^2b-2ab^2-4a^2b+5-2a^2b+3ab^2-12 =ab^2-7 =2*(-1/2)^2-7 =1/2-7 =-13/2