A factor pair is a pair of numbers that, when multiplied will result in a given product ( or the same product ).
For example, the factor pairs of 18 are shown below.
Notice how the product is always 18 or the given number.
Notice also that a factor pair can also include a pair of negative numbers.
Lastly, factor pairs apply only to integers.
Other examples of factor pairs
The factor pairs of 8 are (1,8), (2,4), (-1, -8), and (-2, -4)
The factor pairs of 15 are (1,15), (3,5), (-1, -15), and (-3, -5)
The only factor pairs of 13 are (1, 13) and (-1, -13) since 13 is a prime number.
In fact, any prime number will only have 2 factor pairs.