,若x^2-y^2=0,求分式x^2-3xy+5y^2/3x^2-2xy+4y^2的值请尽快回答

,若x^2-y^2=0,求分式x^2-3xy+5y^2/3x^2-2xy+4y^2的值
请尽快回答

x^2-y^2=0
(x+y)(x-y)=0
x=-y或x=y
当x=-y时
x^2-3xy+5y^2/3x^2-2xy+4y^2
=y^2+3y^2+5y^2/3y^2+2y^2+4y^2
=9y^2/9y^2=1
当x=y时,
x^2-3xy+5y^2/3x^2-2xy+4y^2
=y^2-3y^2+5y^2/3y^2-2y^2+4y^2
=3y^2/5y^2
=3/5