Use the Binomial Theorem to find the coefficient of x' in the expansion of (x+3)" ...-.

Trigonometry (11th Edition)
11th Edition
ISBN:9780134217437
Author:Margaret L. Lial, John Hornsby, David I. Schneider, Callie Daniels
Publisher:Margaret L. Lial, John Hornsby, David I. Schneider, Callie Daniels
Chapter1: Trigonometric Functions
Section: Chapter Questions
Problem 1RE: 1. Give the measures of the complement and the supplement of an angle measuring 35°.
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**Exercise: Binomial Theorem Application**

**Objective:** Use the Binomial Theorem to find the coefficient of \(x^7\) in the expansion of \((x + 3)^{11}\).

\[ \underline{\hspace{20pt}} \]

□ \(x^7\)

**Explanation:**

To solve this problem, apply the Binomial Theorem, which is expressed as:

\[
(x + y)^n = \sum_{k=0}^{n} \binom{n}{k} x^{n-k} y^k
\]

For this specific case:
- \(x\) is \(x\) and \(y\) is \(3\).
- The exponent \(n\) is \(11\).

To find the coefficient of \(x^7\):

1. Set \(n-k = 7\) because we're interested in \(x^7\).
2. Solve for \(k\): \(k = n - 7 = 11 - 7 = 4\).

So we're finding the term where \(k = 4\):

\[
\binom{11}{4} x^{7} \cdot 3^4
\]

\(\binom{11}{4}\) is calculated as:

\[
\binom{11}{4} = \frac{11 \times 10 \times 9 \times 8}{4 \times 3 \times 2 \times 1} = 330
\]

Calculate \(3^4\):

\[
3^4 = 81
\]

Thus, the coefficient of \(x^7\) is:

\[
330 \times 81 = 26,730
\]

Therefore, the coefficient of \(x^7\) in the expansion of \((x + 3)^{11}\) is **26,730**.
Transcribed Image Text:**Exercise: Binomial Theorem Application** **Objective:** Use the Binomial Theorem to find the coefficient of \(x^7\) in the expansion of \((x + 3)^{11}\). \[ \underline{\hspace{20pt}} \] □ \(x^7\) **Explanation:** To solve this problem, apply the Binomial Theorem, which is expressed as: \[ (x + y)^n = \sum_{k=0}^{n} \binom{n}{k} x^{n-k} y^k \] For this specific case: - \(x\) is \(x\) and \(y\) is \(3\). - The exponent \(n\) is \(11\). To find the coefficient of \(x^7\): 1. Set \(n-k = 7\) because we're interested in \(x^7\). 2. Solve for \(k\): \(k = n - 7 = 11 - 7 = 4\). So we're finding the term where \(k = 4\): \[ \binom{11}{4} x^{7} \cdot 3^4 \] \(\binom{11}{4}\) is calculated as: \[ \binom{11}{4} = \frac{11 \times 10 \times 9 \times 8}{4 \times 3 \times 2 \times 1} = 330 \] Calculate \(3^4\): \[ 3^4 = 81 \] Thus, the coefficient of \(x^7\) is: \[ 330 \times 81 = 26,730 \] Therefore, the coefficient of \(x^7\) in the expansion of \((x + 3)^{11}\) is **26,730**.
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