c=2
a^2+b^2=4
x^2/a^2-y^2/(4-a^2)=1
4/a^2-1/3(4-a^2)=1
3a^4-25a^2+48=0
(a^2-3)(3a^2-16)=0
a^2=3 a^2=16/3>4 舍去
b^2=1
双曲线C的方程
x^2/3-y^2=1