已知椭圆a'^2=24,b'^2=20
c'^2=4
c'=2
则a'^2/c'=12
所以准线x=±a^2/c=±12
a^2=12c
e=c/a=1/2
c^2/a^2=1/4
则c^2/(12c)=1/4
c=3
a=2c=6
b^2=a^2-c^2=27
x^2/36+y^2/27=1