x^2+xy-2y^2=0 (x+2y)(x-y)=0 x=-2y或x=y x=-2y 原式=(4y^2-6y^2+3y^2)/(4y^2+y^2)=y^2/5y^2=1/5 x=y 原式=(y^2+3y^2+3y^2)/(y^2+y^2)=7y^2/2y^2=7/2
