Question

已知x^2+2y-2y^2=0则x^2+y^2分之x^2+3 xy+y^2等于ac

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,

Answer 1

(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