已知x+y=5,xy=-6,求3x^2+3y^2

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已知x+y=5,xy=-6,求3x^2+3y^2已知x+y=5,xy=-6,求3x^2+3y^2已知x+y=5,xy=-6,求3x^2+3y^2解3x^2+3y^2=3（x^2+y^2）=3（x^2+

已知x+y=5,xy=-6,求3x^2+3y^2
已知x+y=5,xy=-6,求3x^2+3y^2

已知x+y=5,xy=-6,求3x^2+3y^2
解3x^2+3y^2
=3（x^2+y^2）
=3（x^2+y^2+2xy-2xy）
=3[（x+y）^2-2xy]
=3[（5）^2-2×（-6）]
=3×（25+12）
=3×37
=111.

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