In the given quadratic function,
a
and
c
are constants. The graph of
y
=
f
(
x
)
in the xy-plane is a parabola that opens upward and has a vertex at the point
(
h
,
k
)
, where
h
and
k
are constants. If
k
<
0
and
f
(
−
9
)
=
f
(
3
)
, which of the following must be true?emoji
