Question 259276
f(x)=-x^2+12x+3
you seem to repeat yourself.
The vertex is the max/min. This one has a max at (6,39) which is f(6)=39
so that is three times you ask for the vertex and/or max

All parabolas are symmetric with respect to a line called the axis of symmetry. A parabola intersects its axis of symmetry at a point called the vertex of the parabola.

so that makes four times
The graph doesn't show it well but the peak (vertex is off to the right at 6,39
with x=6 the line of symmetry
*[invoke quadratic "x", -1, 12, 3 ]