Straight line graphs

​​In a nutshell

Straight lines join two points on a coordinate grid and continue past those points infinitely. There are two types of basic straight line graphs: horizontal, and vertical, each recognisable from their equation. 

Definitions

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Equations of the basic straight line graphs

The equation of a horizontal line is 

$$y=c$$

where $$c$$ is the $$y$$-intercept. A vertical line has equation​

​$$x=d$$

where $$d$$ is the $$x$$-intercept.​

Using the equation to draw a basic straight line

To draw either a horizontal or a vertical line using its equation follow this procedure:

procedure

Note: Every point on a horizontal line has the same $$y$$-coordinate and every point on a vertical line has the same $$x$$-coordinate.

Example

Draw the lines $$y=5$$ and $$x=-3$$.

The line $$y=5$$ is horizontal and passes through the point $$(0,5)$$. The line $$x=-3$$ is vertical and passes through $$(-3,0)$$.