【参考答案】
5+7x-6x^2
=-(6x^2 -7x-5)
=-(2x-1)(3x+5)
=(1-2x)(5+3x)
12x^2 +xy-6y^2
=(3x-2y)(4x+3y)
满意敬请采纳,不理解欢迎追问