①(a-2b+3c)²,=a²+4b²+9c²-4ab+6ac-12ac;②（a+b）²(a-b)²-(a-b)(a+b)(a²+b²)=(a+b)(a-b)(a²-b²-a²-b²)=-2b²(a²-b²)=-2a²b²...第一题没有简便一点的吗没办反简便，抱歉