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.
![image](https://img.qammunity.org/2019/formulas/mathematics/college/3intfddsgdv4c4n0zf1dbi1hpetm4s6ss4.png)
So, with b=0, we can plug it back into the first equation to get:
![image](https://img.qammunity.org/2019/formulas/mathematics/college/ehom6he6u6yjrnkhclpo0zqslks39va0j1.png)
So our quadratic is
![(1)/(8)x^2+15](https://img.qammunity.org/2019/formulas/mathematics/college/sqb7oc52zxggm91rdf63p4t3axn9fldoae.png)