Factor Theorem (AQA AS Maths): Revision Note
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Factor Theorem
What is the factor theorem?
The factor theorem is a very useful result about polynomials
A polynomial is an algebraic expression consisting of a finite number of terms, with non-negative integer indices only
![2.5.3 Polynomial not polynomial, Edexcel A Level Maths: Pure revision notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/05/2.5.3-Polynomial-not-polynomial.png)
At A level you will most frequently use the factor theorem as a way to simplify the process of factorising polynomials
![2.5.3 Factorised Polynomial Illustration, Edexcel A Level Maths: Pure revision notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/05/2.5.3-Factorised-Polynomial-Illustration.png)
What do I need to know about the factor theorem?
For a polynomial f(x) the factor theorem states that:
If f(p) = 0, then (x - p) is a factor of f(x)
AND
If (x - p) is a factor of f(x), then f(p) = 0
![2.5.3 Factor Theorem Illustration, Edexcel A Level Maths: Pure revision notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/05/2.5.3-Factor-Theorem-Illustration.png)
Examiner Tips and Tricks
In an exam, the values of p you need to find that make f(p) = 0 are going to be integers close to zero.
Try p = 1 and -1 first, then 2 and -2, then 3 and -3
It is very unlikely that you'll have to go beyond that.
Worked Example
![2.5.3 Factor Theorem Example, Edexcel A Level Maths: Pure revision notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/05/2.5.3-Factor-Theorem-Example.png)
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