若m+n=3,则2m²+4mn+2n²-6的值为——

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若m+n=3,则2m²+4mn+2n²-6的值为——
若m+n=3,则2m²+4mn+2n²-6的值为——

若m+n=3,则2m²+4mn+2n²-6的值为——
2m²+4mn+2n²-6
=2(n+m)²-6
=2x3²-6
=18-6
=12

2m²+4mn+2n²-6
=2（m²+2mn+n²）-6
=2（m+n）²-6
=2*9-6
=12