writing an equation for a quadratic function

G

Guest

Guest
I was given a graph of a quadratic function and told to write an equation for it.

I know that a quadratic function is f(x) = ax^2 + bx + c, and I've looked through all of my notes from the past year over and over, but I have no idea how to write a quadratic equation using the graph of the function. I don't even remember what a, b, and c stand for.

Could somebody please help me?

Thanks!
 
The "a", "b", and "c" just stand for the numbers in those places in the quadratic. (Remember the Quadratic Formula?)

Find the coordinates of three points from the graph. Plug the (x,y) points into the general quadratic equations, "y = ax^2 + bx + c", for x and y. This will give you three linear equations in the variables a, b, and c.

Solve the system of linear equations, using whatever method they have taught you.

Eliz.
 
Top