Reflection: y-axis

How to find the image under the reflection in the y-axis: formula, 3 examples, and their solutions.

Formula

Formula

The image of a point (x, y)
under the reflection in the y-axis is
(-x, y).

Change the sign of x.

Example 1

Example

Solution

The image of (3, 2) is
under the reflection in the y-axis.

Then the image point is,
change the sign of x,
(-3, 2).

So (-3, 2) is the answer.

Graph

This is the graph of (3, 2)
and its image
under the reflection in the y-axis:
(-3, 2).

Example 2

Example

Solution

The image of (-4, -5) is
under the reflection in the y-axis.

Then the image point is,
change the sign of x,
(4, -5).

So (4, -5) is the answer.

Graph

This is the graph of (-4, -5)
and its image
under the reflection in the y-axis:
(4, -5).

Example 3

Example

Solution

The image of [y = 2x + 1] is
under the reflection in the y-axis.

Then the image function is,
change the sign of x,
y = 2(-x) + 1.

2(-x) = -2x

So [y = -2x + 1] is the answer.

Graph

This is the graph of [y = 2x + 1]
and its image
under the reflection in the y-axis:
y = 2(-x) + 1.