请化简以下两道题（a+2b)(a-2b)-1/2b(a-8b)(a+b)²+(a-b)(2a+b)-3a

﹙1﹚=a²-4b²-1/2ab+4b²
=a²－1/2ab
﹙2﹚=a²＋b²＋2ab＋2a²－2ab＋ab－b²－3a²
=ab
=(-2－√3)(√3－2)
=1