Answer
$$(y+1)^2=-\frac{1}{2}(x-3)$$
Work Step by Step
As we are given that the parabola is passing through a point $(-15,2)$ so, $x=-15$ and $y=2$
Therefore, the equation of a parabola is:
$(2+1)^2=4p(-15-3)$
or, $p=-\frac{1}{8}$
Hence, $$(y+1)^2=-\frac{1}{2}(x-3)$$