Examine the quadratic model; the formula is the following: ax^2 + bx + c = 0
Assume or obtain the values for a, b and c. In this case, assume they are 2, -3 and 1; the value of "a" must not equal 0. Solve for x using the quadratic formula.
x = - b +- [(b^2 - 4ac)]^(1/2) / (2a)
In the equation, the +- means "plus or minus".
x = -(-3) +- [(-3^2 - 4(2)(1)]^(1/2) / 2(1)
x = 2.5 or 3.5
Use the x values to plot the intercepts of the curved line. In this case, there are intercepts at (2.5, 0) and (3.5,0).
Plug other x values into the quadratic formula to solve for other points on the line. The equation based on the a, b and c values is the following: 2x^2 - 3x + 1.