12(a²b-3分之1ab²)+5(ab²-a²b)-4(2分之1a²b+3) =12a²b-4ab²+5ab²-5a²b-2a²b-12 =5a²b+ab²-12 =5×(1/5)²×(-5)+(1/5)×(-5)²-12 =(-1)+5-12 =-8,4,看图 ,1,12(a^2b-3分之1ab^2)+5(ab^2-a^2b)-4(2分之1a^2b+3)其中a=5分之1 b=-5先化简再求值