The axis of a parabola is directly in it's center, where the vertex (the most extreme point of the parabola, right where it curves, is). Because all parabolas are symmetrical, it is easier to graph a parabola once you have the axis because it will be exactly the same on both sides. A quadratic equation is an equation who's graph makes a parabola, and is written as ax^2+bx+c. For example, x^2+8x+16. The x coordinate of the vertex is always -b/2a. The x coordinate for that problem is -8/2(1). Or -8/2, or -4. The y coordinate can be found by plugging in that value for x. (-8/2)^2 + 3(-8/2) + 9. Y intercept=13. *I think*. Now you have the two coordinates for the vertex, and the axis is the straight line that runs through that point:( -4, 13.)
