(1)3a^2+bc-3ac-ab=(3a^2-3ac)-(ab-bc)=3a(a-c)-b(a-c)=(3a-b)(a-c)(2)a^2m+bn-an-abm=(a^2m-abm)-(an-bn)=am(a-b)-n(a-b)=(am-n)(a-b)(3)4xy-3xz+8y-6z =(4xy-3xz)+(8y-6z)=x(4y-3z)+2(4y-3z)=(x+2)(4y-3z)(4)x^3+3...（5）ab-5bc-20平方+10ac是2a^2吧？？？ ab-5bc-2a^2+10ac =b(a-5c)-2a(a-5c) =(b-2a)(a-5c)