Graph a parabola with axis of symmetry $x = 3,$ an $x$-intercept at $x = -8,$ and $y$-intercept $5.$
x = -8 is one x intercept
The other x intercept is
x = 3 + (3 - - 8) = 3 + 11 = 14
So we have that
P(x) =a ( x + 8) ( x -14)
If the y intercept is 5, then the point (0,5) is on the graph....so.....
5 = a(0 + 8) ( 0 -14)
5 = (8)(-14)a
5 = -112 a
a = -5/112
P(x) = (-5/112)(x + 8) ( x -14)
Here's the graph :