passing through a point

Sub in the poitns given:

3 = 2^2 + 2b +c     and

3 = 4^2 + 4b +c       Now solve for c   (Multiply first equation by -2  then add it to the second equation....you'll find c = 11)

Here's a graph on EP's response: 

I might have to change it, took quite a while!

Same graph.....from Desmos.....