若m+n=3,则2m2+4mn+2n2-6的值为_.

问题描述:

若m+n=3,则2m2+4mn+2n2-6的值为______.

∵m+n=3,
∴2m2+4mn+2n2-6=2(m+n)2-6=18-6=12.
故答案为:12.