1.4(a-3)^2-(a+3)^2
=[2(a-3)+(a+3)][2(a-3)-(a+3)]
=(3a-3)(a-9)
=3(a-1)(a-9)
2.（a+b)^2-9a^2
=(a+b+3a)(a+b-3a)
= (4a+b)(b-2a)
无疑后请采纳.
书山有路勤为径,学海无涯苦作舟.
-----------与君共勉-----------