若m+n=3,则2m²+4mm+2n²-6的值是

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若m+n=3,则2m²+4mm+2n²-6的值是

若m+n=3,则2m²+4mm+2n²-6的值是
若m+n=3,则2m²+4mm+2n²-6的值是

若m+n=3,则2m²+4mm+2n²-6的值是
2m²+4mm+2n²-6=2(m+n)^2-6=2x9-6=12

2m²+4mm+2n²-6
=2(m²+2mm+n²)-6
=2(m+n)²-6
=2×3²-6
=12