Chapter 15: Problem 17
Use the factor theorem to determine whether or not the second expression is a factor of the first expression. Do not use synthetic division. $$8 x^{3}+2 x^{2}-32 x-8, x-2$$
Short Answer
Expert verified
Yes, \( x-2 \) is a factor of \( 8x^3 + 2x^2 - 32x - 8 \).
Step by step solution
01
Verify Factor Condition
The Factor Theorem states that a polynomial function \( f(x) \) has a factor \((x-c)\) if and only if \( f(c) = 0 \). To verify whether \( x-2 \) is a factor of \( 8x^3 + 2x^2 - 32x - 8 \), we will calculate \( f(2) \) and check if it equals zero.
02
Substitution into Polynomial
Substitute \( x = 2 \) into the polynomial \[ f(x) = 8x^3 + 2x^2 - 32x - 8 \]. This gives us \[ f(2) = 8(2)^3 + 2(2)^2 - 32(2) - 8 \].
03
Calculate Powers
Calculate the power terms: \( 2^3 = 8 \) and \( 2^2 = 4 \). Substitute these values back into the expression to get \[ 8(8) + 2(4) - 32(2) - 8 \].
04
Simplify Expression
Carry out the necessary multiplications: \( 8 \times 8 = 64 \), \( 2 \times 4 = 8 \), and \( 32 \times 2 = 64 \). Substitute these results back into the expression to find \[ 64 + 8 - 64 - 8 \].
05
Evaluate the Result
Simplify \( 64 + 8 - 64 - 8 \) which results in \( 0 \). Since \( f(2) = 0 \), according to the Factor Theorem, \( x-2 \) is a factor of the polynomial \( 8x^3 + 2x^2 - 32x - 8 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polynomial Division
Polynomial division is a method used to divide one polynomial by another, similar to how long division is used with numbers. When dividing a polynomial, such as dividing a cubic polynomial by a linear polynomial like \(x-2\), the goal is to see if the divisor (\(x-2\) in this case) divides the polynomial evenly without a remainder. Just like in the original problem, identifying \(x-2\) as a factor means our division will result in a remainder of zero. Polynomial division is often performed to simplify polynomials, solving for roots, or when factoring complex expressions.
- Start with the leading term of the dividend and divide it by the leading term of the divisor.
- Multiply and subtract the result from the original polynomial.
- Repeat the process with the new dividend until you reach a remainder or the quotient is fully simplified.
Factorization
Factorization is a process of breaking down polynomials into simpler factors that, when multiplied together, give the original polynomial. In the exercise, using the Factor Theorem efficiently identifies \(x-2\) as a factor, simplifying the original polynomial into \[ (x-2)(8x^2 + 18x + 4) \] if we were to continue dividing until no further division is possible. Factorization is vital because:
- It enables easier solving of polynomial equations by setting each factor to zero.
- It helps identify roots and solutions of polynomials, which are critical in graphing and solving algebraic problems.
- Factorization assists in simplifying complex polynomial relationships in algebra and calculus.
Mathematical Proof
Mathematical proof is the logical deduction that confirms the truth of a mathematical statement. In the context of the Factor Theorem, a mathematical proof involves verifying the conditions which justify a polynomial's divisibility. Such proof techniques ensure rigorous understanding and acceptance of mathematical results.The Factor Theorem acts as a bridge between polynomials and their factors, offering a succinct way to ascertain factors through substitution.Examples of mathematical proof in polynomial context include:
- Substitute value \(c\) into the polynomial \(f(x)\), and confirm that \(f(c) = 0\) ensures \(x-c\) is a factor.
- Demonstrate that if the remainder \(r(x)\) after division is zero, \(x-c\) is a confirmed factor.
- Use logical sequences and arithmetic verification, as seen in calculating \(f(2) = 0\), providing a complete proof of \(x-2\) as a factor.