6.1 Greatest Common Factor and Factor by Grouping

3 min readjune 24, 2024

polynomials is a key skill in algebra. It's all about breaking down complex expressions into simpler parts. This process helps solve equations and simplify expressions, making math problems easier to handle.

The (GCF) and factoring by grouping are two important techniques. GCF works for polynomials with a common factor, while grouping is useful for longer expressions. Mastering these methods opens doors to solving trickier math problems.

Greatest Common Factor and Factoring by Grouping

Greatest common factor in polynomials

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  • Largest factor that divides all terms in a without leaving a remainder
  • Found by determining the greatest common coefficient and variable factors among the terms
  • Extracting the GCF involves factoring it out from each term in the polynomial
  • Results in the GCF multiplied by the remaining terms in parentheses (ax2+bx=x(ax+b)ax^2 + bx = x(ax + b))
  • Simplifies the polynomial and is the first step in factoring completely
  • Example: 12x3+18x2=6x2(2x+3)12x^3 + 18x^2 = 6x^2(2x + 3), where 6x26x^2 is the GCF
  • can be used to find the GCF of numerical coefficients

Factor by grouping technique

  • Technique used to factor polynomials with four or more terms and no apparent GCF
  • Involves grouping terms into two or more groups that share a common factor
  • Factor out the GCF from each group
  • If the remaining expressions in parentheses are the same for all groups, factor out the common expression
  • The final factored form will have the common expression multiplied by the factors from each group
  • Helps to break down complex polynomials into simpler factors
  • Example: 6x2+3x4x2=3x(2x+1)2(2x+1)=(3x2)(2x+1)6x^2 + 3x - 4x - 2 = 3x(2x + 1) - 2(2x + 1) = (3x - 2)(2x + 1)

Greatest common factor vs factor by grouping

  • GCF method is used when the polynomial has an evident GCF that divides all terms (ax+ay=a(x+y)ax + ay = a(x + y))
    • Suitable for polynomials with two or three terms (binomials and trinomials)
  • is used when the polynomial has four or more terms and no clear GCF
    • Terms are grouped to find common factors (ax+ay+bx+by=(ax+bx)+(ay+by)=x(a+b)+y(a+b)=(a+b)(x+y)ax + ay + bx + by = (ax + bx) + (ay + by) = x(a + b) + y(a + b) = (a + b)(x + y))
  • In some cases, a combination of both methods is necessary
    • Extract the GCF first, if one exists
    • Then apply factor by grouping to the remaining polynomial if it has four or more terms
  • Recognizing the appropriate method saves time and simplifies the factoring process
  • Examples:
    • GCF: 15x225x=5x(3x5)15x^2 - 25x = 5x(3x - 5)
    • Factor by grouping: 2x33x2+4x6=x(2x23x)+2(2x3)=(x+2)(2x23x)2x^3 - 3x^2 + 4x - 6 = x(2x^2 - 3x) + 2(2x - 3) = (x + 2)(2x^2 - 3x)

Factoring Basics

  • Factoring is the process of breaking down a polynomial into simpler expressions
  • are terms with the same variables raised to the same powers
  • Grouping like terms can simplify the factoring process
  • Binomials are expressions with two terms
  • Trinomials are expressions with three terms

Key Terms to Review (14)

Associative Property: The associative property is a fundamental mathematical principle that states the order in which operations are performed does not affect the final result. It allows for the grouping of numbers or variables in an expression without changing the overall value.
Binomial: A binomial is a polynomial expression that consists of two terms, typically connected by addition or subtraction operations. It is a fundamental concept in algebra that is essential for understanding and manipulating polynomial expressions.
Commutative Property: The commutative property is a fundamental mathematical principle that states the order of factors in an addition or multiplication operation does not affect the final result. This property is essential in understanding and manipulating various mathematical concepts, including decimals, real number properties, linear equations, solving formulas, polynomial operations, and factoring techniques.
Distributive Property: The distributive property is a fundamental algebraic rule that states that the product of a number and a sum is equal to the sum of the individual products. It allows for the simplification of expressions involving multiplication and addition or subtraction.
Factor by Grouping: Factor by grouping is a technique used to factor polynomial expressions by identifying common factors among groups of terms and then factoring out those common factors. This method is particularly useful when dealing with polynomials that cannot be easily factored using other methods, such as factoring by common factors or factoring trinomials.
Factoring: Factoring is the process of breaking down a polynomial expression into a product of simpler polynomial expressions. This technique is widely used in various areas of mathematics, including solving equations, simplifying rational expressions, and working with quadratic functions.
Factoring Out: Factoring out is the process of identifying and extracting a common factor from a set of terms or expressions, allowing for the simplification of the original expression. It is a fundamental algebraic technique used to break down more complex expressions into simpler, more manageable forms.
Fundamental Theorem of Algebra: The fundamental theorem of algebra states that every non-constant polynomial equation with complex number coefficients has at least one complex number solution. This theorem is a fundamental result in algebra that connects the properties of polynomials to the nature of the complex number system.
Greatest Common Factor: The greatest common factor (GCF) is the largest positive integer that divides each of the given integers without a remainder. It is a fundamental concept in mathematics that is particularly relevant in the context of fractions, properties of real numbers, and factoring by grouping.
Like Terms: Like terms are algebraic expressions that have the same variable or combination of variables raised to the same power. They can be combined by adding or subtracting their coefficients, as they represent the same quantity in an expression.
Polynomial: A polynomial is an algebraic expression that consists of variables and coefficients, where the variables are raised to non-negative integer powers. Polynomials are fundamental in algebra and play a crucial role in various mathematical topics covered in this course.
Prime Factorization: Prime factorization is the process of expressing a whole number as a product of its prime factors. It involves breaking down a number into a multiplication of prime numbers that, when multiplied together, equal the original number. This concept is fundamental in understanding greatest common factors and factoring by grouping in algebra.
Quadratic Expression: A quadratic expression is a polynomial expression of degree two, containing a variable with the highest exponent being two. These expressions are characterized by their ability to be factored or solved using various algebraic techniques, making them an essential component in the study of algebra.
Trinomial: A trinomial is a polynomial expression with three terms, typically in the form $ax^2 + bx + c$, where $a$, $b$, and $c$ are real numbers. Trinomials play a crucial role in various algebraic operations and applications, including adding and subtracting polynomials, factoring, and solving quadratic equations.
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