# Equation of a line parallel to the x-axis or y-axis

Lesson Objective
This lesson shows you how to determine the equation of a line that is parallel to the x-axis or y-axis.
In this lesson, we will learn how to determine the equation of a line that is parallel to the x-axis or y-axis.

This lesson shows you the concepts that you should know about a line that is parallel to the x-axis or y-axis of the coordinate plane. Also, we will see some examples on determining its equation.

You should proceed by reading the study tips and watch the math video below. After that, you can try out the practice questions.

# Study Tips

Tip #1
For a line that is parallel to the x-axis, the equation for such a line is:

y = b      where b is some constant

Now, notice that b is the value of the
y-coordinate of any point on the line. For example, if b = -2, the equation of the line parallel to the x-axis will be:

y = -2

The math video below will show you the reason behind this.
Tip #2
Similarly, for a line that is parallel to the
y-axis, the equation for such a line is:

x = a   where a is some constant

Also, notice that a is the value of the
x-coordinate of any point on the line. For example, if a = 1, the equation of the line parallel to the x-axis will be:

x = 1

The math video below will show you the reasons behind this.
Tip #3
Usually, the equation of a line parallel to the x-axis is written this way:

y = 1

For some cases, you may come across the equation above written in this form instead:
y -1 = 0

Now, these two equations are in fact the same, this is because if we add +1 to both sides of the equation, we have:

y -1 +1 = 1
y   = 1

So, we can see that there is no difference between these two equations. This explanation also applies to the equation of a line parallel to the y-axis.

# Math Video

Click play to watch video
Math Video Transcript

# Practice Questions & More

Multiple Choice Questions (MCQ)
Now, let's try some MCQ questions to understand this lesson better.

You can start by going through the series of questions equation of a line parallel parallel to the x-axis or y-axis or pick your choice of question below.
1. Question 1 on determining the equation of a line using the coordinates of two points.
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