题目内容：

已知：m+n=3,求多项式2m²+4mn+2n²-3m-3n+1的值

优质解答

m+n=3
m=3-n
2m²+4mn+2n²-3m-3n+1
=2(3-n)²+4n(3-n)+2n²-3(3-n)-3n+1
=18-12n+2n²+12n-4n²+2n²-9+3n-3n+1
=10