分解因式
(1)a3-4a
(2)-a3-2a2-a
(3)6a3-54a
(4)3(x-2y)2-27(3x+y)2
(5)(a2+4b2)2-16a2b2
(6)3a4-
(7)2(x2-3y2)2+24x2y2
(8)x2-10x+24
(9)(a+b)2-4(a+b-1)
(10)(a+b)2+(a-b)2-4ab
(11)a2-2ab+b2-c2
(12)x4-5x2+4.