So, we are given the y intercept, and since we know c is the same as the y value of the y intercept, we know that c=15.
From there we can pick any two of the points given to us to find our a and b.
Let's use (4,17) and (8,23) becase they are whole numbers.

So, with b=0, we can plug it back into the first equation to get:

So our quadratic is
