# Drawing straight line graphs

## In a nutshell

Straight lines can be plotted by joining up points marked on a coordinate grid. Only two points are needed to plot a straight line, but more than two points can be used when sketching a straight line graph to add precision.

## What is a straight line graph?

A graph is a series of points joined up, even if the points are not clearly marked (for example, with a cross). A straight line graph is the same, with the condition that these points sit in-line with each other. Another word for a straight line graph is a "linear" graph.

## Plotting points

Points can be plotted from the origin on a coordinate grid. You move horizontally for the $x$ coordinate value, then vertically for the $y$ coordinate value.

##### Example 1

*Plot the point $(-2,7)$.*

*Starting from the origin, which is at $(0,0)$, move horizontally by $-2$, which means going to the left by $2$. *

*Then, move vertically by $7$, which means going up by $7$. Mark this point:*

## Using only two points

If you plot two points, you can join them up with a straight line. The line should continue infinitely beyond these two points (in theory - obviously you can't actually draw an infinitely long line!).

##### Example 2

*Draw a straight line that connects the points $(1,3)$ and $(4,0)$.*

*Start by plotting these two points:*

*Then join these points up, ensuring the line continues past the two points:*

## Using more than two points

Sometimes you will be asked to plot many points and to join them up with a line. For now, this is how you will plot a straight line graph.

##### Example 3

*Consider the table below, which gives a series of coordinates for points.*

$x$ | $-1$ | $0$ | $1$ | $2$ | $3$ |

$y$ | $-6$ | $-4$ | $-2$ | $0$ | $2$ |

*Plot these points and check that they all sit in a straight line.*

*The points you have are $(-1,-6)$, $(0,-4)$, $(1,-2)$, $(2,0)$ and $(3,2)$. Plotting these and connecting them looks like:*

See that all of these points are indeed in-line with each other.