Answer
$x^2=-16400(y-4100)$
Work Step by Step
We are given that the focus is below the given vertex, thus, $ p$ is the negative of the distance of the satellite from the center of the Earth.
So, $p=-|4000+100|=-4100$
The vertex and focus have a vertical axis.
The vertex is at $(0, 4100)$
Now, we will write the equation for the parabola that has a vertical axis using the vertex and $p$.
$(x-h)^2=4p(y-k)$
$\implies (x-0)^2=(4)(-4100) (y-4100)$
or, $x^2=-16400(y-4100)$
