Topic: Factoring
Subtopic: GCFs & Grouping
Overview
Remember "prime factoring" from an arithmetic class, e.g. 12=2*2*3? Well, that is what we are going to do in this lesson, except with polynomials. Factoring a polynomial is basically "unmultiplying". Whereas distributing takes 7x(2x+3) to 14x2+21x, factoring does this backwards taking 14x2+21x to 7x(2x+3). There are several methods of factoring, but we will start with the GCF method and the grouping method. Two things to keep in mind:
- Always factor the GCF out first - no matter what other methods of factoring might be involved, start with the GCF.
- Grouping method only works when the poly has an even number of terms (usually 4).
- Caution: Expressions can only factored and not solved. The original problem must contain an equals sign (thus be an equation) to be able to be solved for x. This is a very important difference!
Objectives
By the end of this topic you should know and be prepared to be tested on:
- 7.1.1 Recognize the GCF of two (or more) monomials
- 7.1.2 Factor a polynomial by pulling out the GCF
- 7.1.3 Accurately factor out a GCF that is negative
- 7.1.4 Factor a polynomial by the grouping method
Terminology
Define: GCF = greatest common factor
Text Notes
Text:
Intro & Inter Algebra for CS 3ed by Blitzer, sect. 6.1
- All of this section in the text is useful and important!