d the value of k that makes the divisor x - 11 a factor of polynomial x³ - 13x² + 40x + k

Algebra and Trigonometry (6th Edition)
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ChapterP: Prerequisites: Fundamental Concepts Of Algebra
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Problem 1MCCP: In Exercises 1-25, simplify the given expression or perform the indicated operation (and simplify,...
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**Problem Statement:**

Find the value of \( k \) that makes the divisor \( x - 11 \) a factor of the polynomial \( x^3 - 13x^2 + 40x + k \).

**Solution Explanation:**

To determine the value of \( k \) for which \( x - 11 \) is a factor of the polynomial, we use the Factor Theorem. This theorem states that if \( x - c \) is a factor of the polynomial \( f(x) \), then \( f(c) = 0 \).

Here, \( c = 11 \). Thus, we need to evaluate the polynomial at \( x = 11 \) and set it equal to zero:

\[ f(x) = x^3 - 13x^2 + 40x + k \]
\[ f(11) = (11)^3 - 13(11)^2 + 40(11) + k = 0 \]

Calculate:
\[ (11)^3 = 1331 \]
\[ 13(11)^2 = 1573 \]
\[ 40(11) = 440 \]

Substitute back:
\[ 1331 - 1573 + 440 + k = 0 \]

Simplify:
\[ 198 + k = 0 \]

Solve for \( k \):
\[ k = -198 \]

Thus, the value of \( k \) that makes \( x - 11 \) a factor of the polynomial is \( k = -198 \).
Transcribed Image Text:**Problem Statement:** Find the value of \( k \) that makes the divisor \( x - 11 \) a factor of the polynomial \( x^3 - 13x^2 + 40x + k \). **Solution Explanation:** To determine the value of \( k \) for which \( x - 11 \) is a factor of the polynomial, we use the Factor Theorem. This theorem states that if \( x - c \) is a factor of the polynomial \( f(x) \), then \( f(c) = 0 \). Here, \( c = 11 \). Thus, we need to evaluate the polynomial at \( x = 11 \) and set it equal to zero: \[ f(x) = x^3 - 13x^2 + 40x + k \] \[ f(11) = (11)^3 - 13(11)^2 + 40(11) + k = 0 \] Calculate: \[ (11)^3 = 1331 \] \[ 13(11)^2 = 1573 \] \[ 40(11) = 440 \] Substitute back: \[ 1331 - 1573 + 440 + k = 0 \] Simplify: \[ 198 + k = 0 \] Solve for \( k \): \[ k = -198 \] Thus, the value of \( k \) that makes \( x - 11 \) a factor of the polynomial is \( k = -198 \).
**Problem Statement:**

Given the polynomial function \( f(x) = 8x^3 - 5x + k \), determine the value of \( k \) so that \( x + 5 \) is a factor of the polynomial \( f \).

**Solution:**

1. **Synthetic Division Setup:**

   - The goal is to find \( k \) such that \( x + 5 \) (which corresponds to \( x = -5 \)) is a factor. This means the remainder should be zero when dividing the polynomial by \( x + 5 \).

2. **Synthetic Division Process:**

   - Coefficients of the polynomial: \( 8, 0, -5, k \).
   - Use \( -5 \) for synthetic division.

   \[
   \begin{array}{r|rrrr}
    -5 & 8 & 0 & -5 & k \\
      &   & -40 & 200 & -975 \\
    \hline
      & 8 & -40 & 195 & 0 \\
   \end{array}
   \]

3. **Explanation of Steps:**

   - Write the leading coefficient (8) below the line.
   - Multiply -5 (the value used for division) by 8 (the number just written below the line). Write the result, -40, above the line under the next coefficient.
   - Add the result to the next coefficient: 0 + (-40) = -40.
   - Repeat this process: 
     - Multiply -5 by -40 to get 200. 
     - Add to get 195: \( -5 + 200 = 195 \).
     - Multiply -5 by 195 to get -975 and add to \( k \).

4. **Result:**

   - For the remainder to be zero, \( k \) must be 975.
   - Thus, \( k = 975 \) ensures that \( x + 5 \) is a factor of the polynomial.

**Conclusion:**

The required value for \( k \) is 975, ensuring \( x + 5 \) is a factor of \( f(x) \).

**Reference:**
Video explanation for this solution is available [here](https://www.loom.com/share/fc798de56eed4c99905fa6797d62f6e6).
Transcribed Image Text:**Problem Statement:** Given the polynomial function \( f(x) = 8x^3 - 5x + k \), determine the value of \( k \) so that \( x + 5 \) is a factor of the polynomial \( f \). **Solution:** 1. **Synthetic Division Setup:** - The goal is to find \( k \) such that \( x + 5 \) (which corresponds to \( x = -5 \)) is a factor. This means the remainder should be zero when dividing the polynomial by \( x + 5 \). 2. **Synthetic Division Process:** - Coefficients of the polynomial: \( 8, 0, -5, k \). - Use \( -5 \) for synthetic division. \[ \begin{array}{r|rrrr} -5 & 8 & 0 & -5 & k \\ & & -40 & 200 & -975 \\ \hline & 8 & -40 & 195 & 0 \\ \end{array} \] 3. **Explanation of Steps:** - Write the leading coefficient (8) below the line. - Multiply -5 (the value used for division) by 8 (the number just written below the line). Write the result, -40, above the line under the next coefficient. - Add the result to the next coefficient: 0 + (-40) = -40. - Repeat this process: - Multiply -5 by -40 to get 200. - Add to get 195: \( -5 + 200 = 195 \). - Multiply -5 by 195 to get -975 and add to \( k \). 4. **Result:** - For the remainder to be zero, \( k \) must be 975. - Thus, \( k = 975 \) ensures that \( x + 5 \) is a factor of the polynomial. **Conclusion:** The required value for \( k \) is 975, ensuring \( x + 5 \) is a factor of \( f(x) \). **Reference:** Video explanation for this solution is available [here](https://www.loom.com/share/fc798de56eed4c99905fa6797d62f6e6).
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