Question 399291
The desired points (x,y) are on the following ellipse:
{{{(x-5)^2/16  + y^2/12 = 1}}}

12 - 4  = 2a ==> 2a = 8 ==> a  = 4 ==> {{{a^2  =16}}}
==> {{{b^2 = 4^2 - 2^2 = 16 - 4  = 12}}}