若x^2+xy-2y^2=0,则x^2+3xy+y^2/x^2+y^2=?

来源：学生作业帮编辑：作业帮分类：数学作业时间：2024/05/12 17:16:50

若x^2+xy-2y^2=0,则x^2+3xy+y^2/x^2+y^2=?
那个2是平方的意思,斜杠是分号,

(x+2y)(x-y)=0
x=-2y或x=y
x=-2y
原式=(4y²-6y²+y²)/(4y²+y²)
=-y²/5y²
=-1/5
x=y
原式=(y²+3y²+y²)/(y²+y²)
=5y²/2y²
=5/2
所以原式=-1/5或5/2

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