已知非零实数x,y满足:x2+xy-2y2=0,求(x2+3y+y2)/(x2+y2)的值

由x2+xy-2y2=0,x2-y2+xy-y2=0,(x+y)(x-y)+(x-y)y=0,(x-y)(x+2y)=0.得x-y=0或者x+2y=0.1)当x-y=0,x=y.(x2+3y+y2)/(x2+y2)=(x2+3x+x2)/(x2+x2)=(2x2+3x)/(2x2)=1+3/2x;2)当x+2y=0,x=-2y.(x2+3y+y2)/(x2+y2)=(4y2+3y+y2...值是多少？？？？一个方程,有二个求知数,不能求出值!只能简化,算不出值!对不起，题目错啦，不是(x2+3y+y2)/(x2+y2)，正确的是：（x2+3xy+y2）/（x2+y2），前面是对的那后面变为1)当x-y=0,x=y.(x2+3xy+y2)/(x2+y2)=(x2+3x^2+x2)/(x2+x2)=(5x2)/(2x2)=5/2;2)当x+2y=0,x=-2y.(x2+3xy+y2)/(x2+y2)=(4y2-6y2+y2)/(4y2+y2)=(-y2)/(5y2)=-1/5.这样就正确了!