e=c/a=1/2
c^2/a^2=1/4
a^2=4c^2
a^2=b^2+c^2
b^2=3c^2
x2/a2+y2/b2=1
x2/4c^2+y2/3c^2=1
N(2,-3)
4/4c^2+9/3c^2=1
c^2=4
a^2=16
b^2=12
x2/16+y2/12=1
x1+x2=-2
y1+y2+4
x1=-2-x2
y1=4-y2
x2/16+y2/12=1
(-2-x2)^2/16+(4-y1)^2/12=1
x1=(4y1-15)/3
y1=
k=y1/x1
y-2=k(x-x1)