Chapter 5: Problem 46
Factor expression completely. If an expression is prime, so indicate. \(60 q^{2} r^{2} s^{4}+78 q r^{2} s^{4}-18 r^{2} s^{4}\)
Short Answer
Expert verified
The completely factored form is \(6r^2s^4(5q - 1)(2q + 3)\).
Step by step solution
01
Identify the Greatest Common Factor (GCF)
Examine each term in the expression to find the common factors. Each term has a common factor of \(6r^2s^4\). This factor is present because 60, 78, and 18 have a numerical GCF of 6, and all terms have at least \(r^2\) and \(s^4\) as factors. Thus, the GCF is \(6r^2s^4\).
02
Factor out the GCF
Divide each term of the expression by the GCF \(6r^2s^4\) and rewrite the expression. This simplifies to: \[60q^2r^2s^4 + 78qr^2s^4 - 18r^2s^4 = 6r^2s^4(10q^2 + 13q - 3)\]
03
Analyze the Quadratic Expression
The expression \(10q^2 + 13q - 3\) inside the parentheses needs to be examined to see if it can be factored further. Check for possible pairings that give a product of \(-30\) (since \(10\times -3 = -30\)) and a sum of \(13\).
04
Perform Factorization by Grouping
Identify two numbers that multiply to \(-30\) and add to \(13\). These are \(15\) and \(-2\). Use these to break down the middle term: \[10q^2 + 13q - 3 = 10q^2 + 15q - 2q - 3 \]. Regroup and factor by grouping: \[(10q^2 + 15q) + (-2q - 3) = 5q(2q + 3) - 1(2q + 3)\]. Factor out the common term: \[(5q - 1)(2q + 3)\].
05
Write the Entire Factored Expression
Combine all the factored parts together: \[60q^2r^2s^4 + 78qr^2s^4 - 18r^2s^4 = 6r^2s^4(5q - 1)(2q + 3)\].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Greatest Common Factor
The concept of the Greatest Common Factor (GCF) is a fundamental step in breaking down expressions into simpler components. The GCF is the largest expression that can be evenly divided into each term of a polynomial. In our example, to find the GCF, we start by looking at each term:
- Numerical coefficients: 60, 78, and 18 share a greatest common factor of 6.
- Variable components: Each term contains at least one factor of \(r^2\) and \(s^4\).
Quadratic Expressions
Quadratic expressions are polynomials of degree two. They are typically written in the form \(ax^2 + bx + c\), where \(a\), \(b\), and \(c\) are constants. In our original problem, once the GCF \(6r^2s^4\) is factored out, we are left with a quadratic expression \(10q^2 + 13q - 3\). Understanding how to further factor these expressions can simplify them more:
- Identify the product of \(a\) and \(c\), which is \(-30\) (from \(10\times -3\)).
- Find two numbers that multiply to \(-30\) and add to \(b = 13\). This would be 15 and -2.
Factorization by Grouping
Factorization by grouping involves rearranging a polynomial's terms so they can be grouped into factors that can be further simplified. This technique is particularly useful for quadratic expressions like \(10q^2 + 13q - 3\) from our example.To illustrate:
- Start by rewriting the quadratic expression with the middle term split: \(10q^2 + 15q - 2q - 3\).
- Next, group the terms: \((10q^2 + 15q) + (-2q - 3)\).
- Factor each group separately: \(5q(2q + 3) - 1(2q + 3)\).
- Notice \((2q + 3)\) is common, enabling further factorization: \((5q - 1)(2q + 3)\).