The equation of a straight line on a graph is made up of a term, an term and a number, and can be written in the form of .

- The slope of the line is known as the
**gradient**and is represented by the value of in the equation. - The point at which the line
**crosses the****-axis**is the value of in the given equation, and is referred to as the**-intercept**.

All the points that lie on the green line have a -coordinate that is the same as the -coordinate, eg:

and

We say that the equation of the line is .

All the points that lie on the purple line have a -coordinate that is one number higher than the -coordinate of the same line, eg:

and

In other words, the -coordinate equals the -coordinate .

So the equation of the line is .

- Question
What is the equation of the line shown below?

The coordinates of the points are , and .

Here, the value is always twice the value.

The equation of the line that fits these and values is: