Chapter 15: Problem 34
Use the factor theorem and synthetic division to determine whether or not the second expression is a factor of the first. $$t^{5}-3 t^{4}-t^{2}-6 ; t-3$$
Short Answer
Expert verified
The remainder is -15, so \( t-3 \) is not a factor.
Step by step solution
01
Set Up Synthetic Division
To verify if \( t-3 \) is a factor of \( t^{5} - 3t^{4} - t^{2} - 6 \), we first identify our divisor, which is \( t-3 \). This gives us the root \( t = 3 \) to use for synthetic division. We will perform synthetic division using the coefficients of the terms of our polynomial: 1 (for \( t^5 \)), -3 (for \( t^4 \)), 0 (for \( t^3 \), not explicitly present), -1 (for \( t^2 \)), 0 (for \( t^1 \), not explicitly present), and -6 (for the constant term).
02
Perform Synthetic Division
Write down the root 3 outside a synthetic division grid. Start with the leading coefficient, 1, and bring it straight down. Multiply 3 by 1 and write the result beneath the next coefficient (-3), then sum them: \(-3 + 3 = 0\). Continue this process, always multiplying by 3 and adding the result to the next coefficient, repeating through all coefficients: \( (0 \cdot 3) + 0 = 0 \), \( (0 \cdot 3) + (-1) = -1 \), \((-1 \cdot 3) + 0 = -3 \), and \((-3 \cdot 3) + (-6) = -15\).
03
Analyze the Remainder
The results of synthetic division are the new coefficients for the polynomial obtained by division, but the last number is the remainder. For \( t-3 \) to be a factor, the remainder must be 0. The remainder from our division, -15, indicates that \( t-3 \) is not a factor of \( t^{5} - 3t^{4} - t^{2} -6 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Factor Theorem
The Factor Theorem is a fundamental theorem in algebra that connects roots of a polynomial to its factors. It states that a polynomial \( f(t) \) has a factor \( t-a \) if and only if \( f(a) = 0 \). This means that if, after substituting \( a \) into the polynomial, the result is zero, \( t-a \) is indeed a factor. To apply this theorem, first identify the value of \( a \) from \( t-a \), which will be our test value for the polynomial. In our problem, we replace \( t \) with 3, because the divisor is \( t-3 \). Substituting 3 into the polynomial, we compute \( 3^5 - 3 \, (3^4) - 3^2 - 6 \). If the result is zero, \( t-3 \) is a factor; if not, it isn't. This aligns directly with the essence of the Factor Theorem.
Synthetic Division
Synthetic division is a shortcut method of polynomial division, especially useful when dividing by linear factors. It simplifies the process by focusing on coefficients. Here's how it works:
- Write the coefficients of the polynomial in descending order, filling in zeros for missing terms.
- Place the root (from \( t-a \)) to the left of the coefficients. In this case, it's 3 because of \( t-3 \).
- Bring down the leading coefficient to the bottom row.
- Multiply this coefficient by the root and add it to the next coefficient.
- Repeat the process for each coefficient, continually multiplying by the root and adding, until all coefficients are processed.
Roots of Polynomials
Finding the roots of a polynomial is equivalent to solving when the polynomial equals zero. These roots are significant because each root represents a solution to the polynomial equation and can also indicate factors according to the Factor Theorem.When using synthetic division or evaluating a polynomial for possible roots, focus on substituting values derived from potential linear factors. In the problem at hand, if \( t=3 \) were a root, then \( t-3 \) would be a factor, as the polynomial would equate to zero for \( t=3 \).However, for this polynomial, \( 3 \) is not a root, indicated by the non-zero remainder when using synthetic division: \(-15\). Therefore, there's no zero at \( t=3 \), and \( t-3 \) is not a root. Understanding this intertwined relationship between roots and polynomial factors is crucial for solving polynomial equations effectively.