Factors
In general, a factor of a number is a number that can be multiplied by another number to get . But, the definition changes a little according to what kind of math you're doing.
For whole numbers and :
We say is a factor of if for some whole number .
For example, is a factor of , since .
But is not a factor of , since there is no whole number for which .
For polynomials and :
We say is a factor of if for some polynomial .
For example, is a factor of , since
.
But is not a factor of , since there is no polynomial for which .
Common Factors
If two numbers (or polynomials) have a factor in common, then it is called a common factor.
For instance, the numbers and have as a common factor.
The polynomials
and
have as a common factor.