2(2A+B)-3(A+B) =4A+2B-3A-3B =A-B =5a^3b+2a^4-3a^2b-ab^3 -(6ab^3-8a^3b+3a^4-5b^4) =-a^4+13a^3b-3a^2b-7ab^3+5b^48u0i5f8h2j9g5u3u1f5u7f8y5d1＝5h6g8u对吗？