1. 用提公因式法分解因式:
(1)$mx+my$; (2)$m^{2}n-3mn$;
(3)$2a^{3}-8a^{2}b+8ab$; (4)$3x^{3}-15x^{2}-24x$;
(5)$24x^{2}y+36xy^{2}-28y^{3}$; (6)$-9ma^{3}+27ma^{2}-72ma$.
答案：1.(1)m(x+y) (2)mn(m-3)
(3)2a(a2-4ab+4b) (4)3x(x2-5x-8)
(5)4y(6x2+9xy-7y2) (6)-9ma(a2-3a+8)
2. 把下列各式分解因式:
(1)$2m(x-y)-3n(x-y)$; (2)$(a-3)^{2}+(3-a)$;
(3)$x(a-b)+y(b-a)-3(b-a)$; (4)$(x-y)^{3}+4x(x-y)^{2}$;
(5)$-18a^{3}+12a^{2}-2a$; (6)$6(x+y)^{2}-2(x-y)(x+y)$;
(7)$(2a-b)(3a-2)+b(2-3a)$.
答案：2.(1)(x-y)(2m-3n) (2)(a-3)(a-4)
(3)(a-b)(x-y+3) (4)(x-y)2(5x-y)
(5)-2a(3a-1)2 (6)4(x+y)(x+2y)
(7)2(3a-2)(a-b)
