Answers may vary. $y=-x^2+4$
Work Step by Step
The graph above has a maximum value at $x=0$. Line of symmetry: $x=-b/2a$ $x=-0/2*-1$ $x=0$ $y=-x^2+4$ $y=-0^2+4$ $y=0+4 = 4$ Line of symmetry is at $x=0$ and goes through $(0,4)$. Since the graph opens down, we know this point is a maximum.