已知x+2y=0,xy不=0,求分式(x^2+2xy-y^2)/(2x^2+xy+y^2)的值
问题描述:
已知x+2y=0,xy不=0,求分式(x^2+2xy-y^2)/(2x^2+xy+y^2)的值
答
x+2y=0,x=-2y
(x^2+2xy-y^2)/(2x^2+xy+y^2)=(4y^2-4y^2-y^2)/(8y^2-2y^2-y^2)=-y^2/5y^2=-1/5