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The coordinate plane is a two-dimensional surface where you can plot points, lines, and curves to represent mathematical equations visually. It comprises two number lines that intersect at a right angle:
The horizontal number line is called the x-axis.
The vertical number line is called the y-axis.
The point where the x-axis and y-axis meet is known as the origin, denoted by (0,0). Distances to the right of the origin are positive on the x-axis, while distances to the left are negative. Similarly, distances above the origin are positive on the y-axis, and distances below are negative. Each point on the plane can be described with a pair of coordinates (x, y), where 'x' represents the horizontal position, and 'y' represents the vertical position.

A horizontal line equation looks like this: y = c, where 'c' is a constant. This tells you that no matter what value 'x' takes, 'y' remains the same. In other words, every point on a horizontal line has the same y-coordinate.
For the equation y = 3, the line is horizontal and always three units above the x-axis. Here, '3' is the value of 'y' everywhere along the line. You can think of it this way:

• If x = -2, then y = 3.
• If x = 0, then y = 3.
• If x = 4, then y = 3.

No matter what value 'x' takes, 'y' is always 3.

Plotting a horizontal line equation like y = 3 is straightforward. Follow these simple steps:

• Locate the y-coordinate '3' on the y-axis.
• Draw a small mark or point at this location.
• Draw a straight line through this point, extending it infinitely in both directions along the x-axis.

Remember, because the value of 'y' is constant and does not depend on 'x,' the line is horizontal. This visual representation helps you understand that for any x-value, the y-coordinate remains 3.
Horizontal lines are unique because they don't tilt up or down but remain parallel to the x-axis. This simplicity makes them easy to understand and plot.