联立两直线方程,得中点坐标为(2/3,1/3)
k=-(b^2×x)/(a^2×y)=-(2×b^2)/(a^2)=-1
a^2=2b^2
c^2=a^2-b^2
c^2/a^2=b^2/a^2=1/2
e=c/a=根号二/2