解
6mx²+4nxy+2x+2xy-x²+3
=(6m-1)x²+(4n+2)xy+2x+3
不含二次项
∴6m-1=0,4n+2=0
∴m=1/6,n=-1/2
∴6m+2n-2
=6×(1/6)+2×(-1/2)-2
=1-1-2
=-2