6mx²+4nxy+2x+2xy-x²+y-4
=(6m-1)x²+(4n+2)xy +2x+y-4
由题干知:该多项式不含二次项
那么6m-1=0,4n+2=0
则
6m-2n+2
=(6m-1)-(1/2)(4n+2)+4
=4