x²+xy-2y²=0,(x+2y)(x-y)=0x=-2y或x=y所以1.x=-2y3x²+xy+6y²/x²+y²=（12y²-2y²＋6y²）/(4y²＋y²)=16/52.x=y原式=(3+1+6)/2=5