2x^2-5xy-3y^2=0
(x-3y）（2x+y）=0
x=3y x= -0.5y
代入x^2-2xy-y^2=1中解得y=±√2/2 ；y=±2
代入x=3y x= -0.5y中解得x=±3√2/2；x=±1