Factored Form
Writing Equations
Since the factored form shows the x -intercepts of the function, it is possible to write an equation in factored form if you know the x -intercepts. Substitute values into the form: 
and simplify.
and simplify.Example Model the quadratic function graphed below using an equation in factored form.
Step 1. Find the x-intercepts.
The x-intercepts of the graph are (0, 0) and (4, 0).
Step 2. Substitute the x-intercepts into the general form.
Step 3. Substitute another point from the graph into the general form and solve for the a-value.
Step 4. Substitute the a-value into the formula.
