IXL - Characteristics of quadratic functions: equations (Algebra 2 practice)

or

Find
the
equation
of
the
axis
of
symmetry
for
the
parabola
y = x²
.

Simplify any numbers and write them as proper fractions, improper fractions, or integers.

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or

Learn with an example

question

Find
the
equation
of
the
axis
of
symmetry
for
the
parabola
y = x² − 4x − 2
.

Simplify any numbers and write them as proper fractions, improper fractions, or integers.

key idea

Every parabola has an axis of symmetry. This line passes through the vertex and divides the parabola into two halves that are mirror images.

The
equation
of
the
axis
of
symmetry
for
the
parabola
y = ax² + bx + c
is
x
=
^–b
2a
.

solution

To find the equation of the axis of symmetry, start by locating a and b in the given equation.

y

=

x

²

−

4

x

−

2

=

1

x

²

+

^–4

x

+

^–2

Next
plug
a
=
1
and
b
=
^–4
into
the
equation
of
the
axis
of
symmetry.

x

=

^–b

2a

=

^–(^–4)

2(1)

Plug
in
a = 1
and
b = ^–4

=

4

2

Multiply

=

2

Simplify

So,
the
equation
of
the
axis
of
symmetry
is
x = 2
.

Looking for more? Try these:

Lesson: Quadratic functions

or

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Not feeling ready yet? These can help:

I.1Coordinate plane review

L.12Equations of horizontal and vertical lines

N.1Characteristics of quadratic functions: graphs

Lesson: Quadratic functions