What is the equation of the axis of symmetry for a parabola?

Relevant page
<a href="/quadratic-equations/4-graph-quadratic-function.php">4. The Graph of the Quadratic Function</a>
What I've done so far
I couldn't find it anywhere.

Re: Equation of the axis of symmetry for a parabola?

The first one has axis of symmetry `x = -1` It looks like this:

The second has axis of symmetry `x = 1.25`

You can work it out using the formula for the vertex given:

`x = -\frac{b}{2a}`

Hope that helps.

X

Hi Sharon
The axis of symmetry of a parabola passes through the vertex (pointy bit) of the parabola and it divides the parabola exactly in half.
For the simple parabola
`y = x^2`,
the axis of symmetry is the y-axis (whose equation is `x = 0`).
See the examples on this page: <a href="/quadratic-equations/4-graph-quadratic-function.php">4. The Graph of the Quadratic Function</a>
The first one has axis of symmetry `x = -1` It looks like this:
[graph]310,250;-5.3,5.3;-4.3,10.3,1,2;x^2+2x-3[/graph]
The second has axis of symmetry `x = 1.25`
[graph]310,250;-5.3,5.3;-4.3,10.3,1,2;-2x^2+5x+3[/graph]
You can work it out using the formula for the vertex given:
`x = -\frac{b}{2a}`
Hope that helps.

Re: Equation of the axis of symmetry for a parabola?

In this case, we'll have `a=1`, `b=2` and `c=3`. So what will the axis of symmetry be?

X

This is a parabola on its "side".
[graph]310,250;-3.3,5.3;-4.3,3;1,2;y^2+2y+3[/graph]
In this case, we'll have `a=1`, `b=2` and `c=3`. So what will the axis of symmetry be?

Re: Equation of the axis of symmetry for a parabola?