Chapter 0: Problem 67
31–76 ? Factor the expression completely. $$ y^{3}-3 y^{2}-4 y+12 $$
Short Answer
Expert verified
The completely factored form is \((y - 2)(y + 2)(y - 3)\).
Step by step solution
01
Group the terms
The expression is \( y^3 - 3y^2 - 4y + 12 \). Begin by grouping the first two terms together and the last two terms together: \( (y^3 - 3y^2) + (-4y + 12) \).
02
Factor each group
Factor out the greatest common factor from each group. For \( y^3 - 3y^2 \), factor out \( y^2 \): \( y^2(y - 3) \). For \(-4y + 12\), factor out \(- 4\): \(-4(y - 3) \).
03
Factor out the common binomial
Both groups now have a common binomial factor of \( (y - 3) \). Factor this out of the expression: \((y^2 - 4)(y - 3)\).
04
Factor the difference of squares
The expression \( y^2 - 4 \) is a difference of squares, as \(y^2 - 4 = (y - 2)(y + 2)\). Thus, factor it further: \( (y - 2)(y + 2)(y - 3) \).
05
Write the completely factored expression
Combine all the factored parts to write the completely factored expression: \( (y - 2)(y + 2)(y - 3) \). This is the completely factored form of the original expression.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Grouping Method
The grouping method is a handy technique in polynomial factoring. It's especially useful when dealing with four-term polynomials. The key idea is to rearrange the terms in pairs and factor them piece by piece.
Let's break it down:
Let's break it down:
- Identify and group terms: Divide the polynomial into two groups based on common traits or similar expressions.
- Factor each group separately: Look for any common factors within each group. This allows you to simplify the polynomial even further.
- Combine factors: Look for a common factor between the newly factored groups and combine them.
Greatest Common Factor
The Greatest Common Factor (GCF) plays a pivotal role in polynomial factoring. It is the largest factor that divides each term in the group without a remainder, simplifying the polynomial.
To use the GCF in factoring:
To use the GCF in factoring:
- Identify the GCF: Look at each group of terms and find the highest power of variables and the largest constant that divide each term.
- Factor out the GCF: Divide each term by the GCF and place the GCF outside the parentheses.
- Simplify the expression: Rewrite the expression using the new factors.
Difference of Squares
Understanding the difference of squares is essential for polynomial factoring. A difference of squares is a specific pattern where two terms, each being a square, are subtracted. The formula is: \[ a^2 - b^2 = (a-b)(a+b)\] This form allows for straightforward factoring.
To apply the difference of squares:
To apply the difference of squares:
- Recognize the pattern: Ensure the expression fits \( a^2 - b^2 \).
- Factor accordingly: Write the expression as \( (a-b)(a+b) \).
- Check your work: Ensure both resulting binomials multiply back to the original expression.