## Key Stage 4

### Meaning

When a relationship between two variables is **linear** they increase by a constant amount in relation to one another.

### About Linear Relationships

- A scatter graph showing a
**linear**relationship has straight line of best fit. - On a
**linear graph**; when one variable increases, the other increase or when one increases the other decreases. - A
**linear relationship**may have a non-zero y-intercept. - If the line of best fit on for a
**linear relationship**has a y-intercept of zero then it is called 'directly**proportional**'.

### Examples

This scatter graph shows a linear relationship where x increases and y increases.
\(y = mx + c\) Where m, the gradient, is positive. |
This scatter graph shows a linear relationship where x increases and y decreases.
\(y = mx + c\) Where m, the gradient, is negative. |
This scatter graph shows a linear relationship that is directly proportional where x doubles, y doubles.
\(y = mx\) Where m, the gradient, is positive. |