Picture of the axis of symmetry
Every parabola has an axis of symmetry which is the line that divides the graph into two perfect halves.
On this page, we will practice drawing the axis on a graph, learning the formula, stating the equation of the axis of symmetry when we know the parabola's equation
Explore how the graph and equation relate to the axis of symmetry, by using our interactive program below.
It is the line $$ x = 2 $$
It is the line $$ x = -1 $$
There are two different formulas that you can use to find the axis of symmetry. One formula works when the parabola's equation is in vertex form and the other works when the parabola's equation is in standard form .
Explore the relationship between the axis of symmetry and graph of a parabola by changing the values of a, b and c of the parabola plotter below
of symmetry from Vertex Form Equation
Since this equation is in vertex form,use the formula $$ x = h $$
The line $$ x = -3 $$ is this parabola's axis of symmetry.
Since this equation is in vertex form, use the formula $$ x = h$$
The axis of symmetry is the line $$ x = 3$$
finding axis of symmetry from Standard Form
Since this equation is in standard form, use the formula for standard form equation $$ x = \frac{ -b}{ 2a} $$
Answer: the axis of symmetry is the line $$ x = 1 $$
Since this equation is in standard form, use the formula for standard form equation x = -b/2a
Answer: the axis of symmetry is the line x = 2
