The equation of a parabola in vertex form is:

Where (h,k) are the coordinates of the vertex of the parabola.
From the picture, notice that the vertex of the parabola has coordinates (3,23), then:

Then, our function reduces to:

Evaluate the function at x=0 to find the value of a. Notice from the figure that f(0)=14. On the other hand:

Since f(0)=14 then:

Therefore, the function that describes this situation is:
