**Ordered pair**
- Any two numbers where the order is important

For example, (2,3) is an ordered pair. It gives the location of the point.

The point A is located 2 units in the x-direction and 3 units in the y-direction.

The point B is located 1 unit in the negative x-direction and 2 units in the negative
y-direction.

In other words,** in an ordered pair, the first number gives the number of units
along the x-axis and the second number gives the number of units along the y-axis.**

**Relation **-
A relation is a set of ordered pairs, can be set out in a table or can be listed as a set
of ordered pairs.

For example:

This is a relation set out as a set of ordered pairs.

{(1,5) (2,10) (3,15) (4,20) (5,25)} is a relation.

The same relation can be set out in a table.(as below)

*x* |
1 |
2 |
3 |
4 |
5 |

*y* |
5 |
10 |
15 |
20 |
25 |

The **domain **of the
relation is {1, 2, 3, 4, 5},which are the first-named numbers.

The **range** of the
relation is {5, 10, 15, 20, 25}, which are the second-named numbers.

The **rule or equation**
is how the numbers are related to each other.

In the above relation, we can write the rule as, *y* = 5 ×* x *or*
y = 5x.*

This is a linear relationship.

**x**-**intercepts** are where the graph cuts the *x* axis.

**y**-**intercepts** are where the graph cuts the *y* axis.

The gradient of line AB is the slope of the line, which is equal to the
ratio between the

vertical distance(rise) and the horizontal distance(run).

Vertical distance = 5units,
Horizontal
distance = 3units

rise = 5units,
run = 3units