若m+n=3,则2m²+4mn+2n²-6的值为( ) A.12 B.6 C.3 D.0

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若m+n=3,则2m²+4mn+2n²-6的值为( ) A.12 B.6 C.3 D.0
若m+n=3,则2m²+4mn+2n²-6的值为( ) A.12 B.6 C.3 D.0

若m+n=3,则2m²+4mn+2n²-6的值为( ) A.12 B.6 C.3 D.0
m+n=3
2m²+4mn+2n²-6
=2(m²+2mn+n²)-6
=2(m+n)²-6
=18-6
=12

2m²+4mn+2n²-6
=2(m+n)^2-6
=2x9-6
=12