把下列各式分解因式: (1)x 6 -81x 2 y 4 (2)2x 2 -x-3 (3)x 2 -7x-8 (4)a 3 -2a 2 +a (5)a 2 +6a+5 (6)7x 2 +13x-2 (7)-x 2 +4x+5 (8)-3x 2 +10x+8 (9)x 3 z-4x 2 yz+4xy 2 z (10)x 3 z-4x 2 yz+4xy 2 z (11)x 4 +6x 2 +9 (12)(x-1) 2 -4(x-1)y+4y 2 (13)(x 2 -10)(x 2 +5)+54 (14)(a-b)(x-y)-(b-a)(x+y) (15)4m 5 +8m 3 n 2 +4mn 4 (16)4a 2 +4ab+b 2 -1 (17)x 3 -x 2 -2x+2.