-1/3x^2a+2y^2与3x^4y^b是同类项
则,2a+2=4,
得a=1
b=2
2a^b-[2a^3+(5a^2*b-3ab^2)-2(a^3+2a^2*b-ab^2)]
=2-[2+(10-12)-2(1+4-4)]
=2-(-2)
=4