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The rectangular coordinate system (or Cartesian coordinate system) is a way to pinpoint where you are on a map or graph using two different values. These two values, usually referred to as 'x' and 'y,' can help you locate any point on a plane. The 'x' value shows how far left or right you need to slide from the origin (which is the center of the plane, known as (0,0)). The 'y' value shows how far up or down to move.
When you start graphing equations, you'll need this system to place points accurately.
If you're given an equation like the one in our exercise, y - 1 = 0, you can use the rectangular coordinate system to draw its graph.
Remember, while the x-axis runs horizontally and represents 'x' values, the y-axis runs vertically and stands for 'y' values.

A single-variable linear equation means there's only one variable involved. In this exercise, our variable is 'y.' These equations are usually very easy to solve and graph.
Look at y - 1 = 0. This tells us one thing: the value 'y' minus 1 is zero. To get 'y' by itself, just add 1 to both sides. This makes the equation: y = 1.
Whenever you see an equation like y = 1, it means no matter what 'x' is, 'y' will always be equal to 1. It's a very straightforward relationship, and it makes graphing simpler.

A horizontal line is a straight line that goes from left to right or right to left and is parallel to the x-axis. It means that no matter where you are along this line, the y-value remains the same.
In our exercise, after solving y - 1 = 0, we found that y = 1. This tells us that for any value of x, y will always be 1.
To graph y = 1, find the point on the y-axis where y equals 1. Then, draw a straight line across that doesn’t slant up or down. This is your horizontal line.
This line is parallel to the x-axis and shows an unchanging y-value.
This is how you represent equations that tell you y is constant, regardless of x.