3xy-2x-12y+8 =(3xy-12y)-(2x-8) =3y(x-4)-2(x-4) =(x-4)(3y-2) ab-5bc-2a+10ac =(10ac-5bc)-(2a-ab) =5c(2a-b)-a(2a-b) =(2a-b)(5c-a) 5ac+7ay-5bc-7by =(5ac-5bc)+(7ay-7by) =5c(a-b)+7y(a-b) =(a-b)(5c+7y) xy+3x-2xy-6y =(xy-2xy)+(3x-6y) =xy(x-2y)+3(x-2y) =(x-2y)(xy+3) 7x-3y+xy-21x =7x-21x-3y+xy =(7x-21x)+(xy-3y) =7x(x-3)+y(x-3) =(x-3)(7x+y) 3a^2+bc-3ac-ab =(3a^2-3ac)+(bc-ba) =3a(a-c)+b(c-a) =3a(a-c)-b(a-c) =(3a-b)(a-c) a^2m+bn-an-abm =am(a-b)-n(a-b) =(am-n)(a-b) 第五题的题目有错
几道因式分解的题目.进来一定要做做,我急.谢谢了///如题