Find expressions for the quadratic functions whose graphs are shown.
The normal form we work with discussing parabolas is . You need to find what "a" and "c" are. You have two variables and two points to work with. That's enough to solve for each variable.
EDIT: Big mistake, my apologies. See below post to clarify.
Since you have the point (4,2) you can deduce that there is also the point (2,2) on the graph. Now you plug in your three (x,y) pairs into the equation I wrote above and solve for your a, b and c.