Chapter 5: Problem 72
Factor each polynomial completely. $$3 x^{3}-27 x$$
Short Answer
Expert verified
The completely factored form is \(3x(x - 3)(x + 3)\).
Step by step solution
01
Identify the Greatest Common Factor (GCF)
Find the greatest common factor of the terms in the polynomial. The terms are \(3x^3\) and \(-27x\). The GCF is \(3x\).
02
Factor Out the GCF
Factor out the greatest common factor from the polynomial. This gives us: \(3x(x^2 - 9)\).
03
Recognize the Difference of Squares
Notice that the expression \(x^2 - 9\) is a difference of squares. Recall that \(a^2 - b^2 = (a - b)(a + b)\). Here \(a = x\) and \(b = 3\).
04
Factor the Difference of Squares
Apply the difference of squares formula. \(3x(x^2 - 9) = 3x(x - 3)(x + 3)\).
05
Write the Final Factored Form
The completely factored form of the polynomial is \(3x(x - 3)(x + 3)\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Greatest Common Factor (GCF)
The Greatest Common Factor (GCF) is a critical concept in polynomial factorization. It is the largest factor shared by all terms in the polynomial.
To find the GCF, follow these steps:
To find the GCF, follow these steps:
- List the factors of each term.
- Select the largest common factor.
- For \(3x^3\), the factors are 3, x, x, and x.
- For \(-27x\), the factors are -27, x, and its numerical factorization (-27 = -3 × 3 × 3).
Difference of Squares
The Difference of Squares is a specific factoring pattern in which a polynomial can be expressed as two squared terms subtracted from one another, i.e., \(a^2 - b^2\).
When identified, it can be factored into: \[(a-b)(a+b)\].
Let’s apply this to our exercise's polynomial:
After factoring out the GCF, we have \(3x(x^2 - 9)\). Notice that \(x^2 - 9\) is a difference of squares:
When identified, it can be factored into: \[(a-b)(a+b)\].
Let’s apply this to our exercise's polynomial:
After factoring out the GCF, we have \(3x(x^2 - 9)\). Notice that \(x^2 - 9\) is a difference of squares:
- \(x^2 = (x)^2\)
- \(9 = (3)^2\)
Algebraic Expressions
Understanding Algebraic Expressions is essential for mastering polynomial factorization. An algebraic expression is a combination of variables, numbers, and operators. Consider the parts in our polynomial:
- Coefficians are 3 and -27
- Variables are x
- Exponentials like \(x^3\)
- Finding the GCF
- Recognizing special patterns (like difference of squares)
- Rewriting the expression in simpler terms
- Identifying the GCF which is \(3x\)
- Factoring out the GCF: \[3x(x^2 - 9)\]
- Finding the difference of squares: \[x^2 - 9 = (x - 3)(x + 3)\]
- Combining all factors: \[3x(x - 3)(x + 3)\]