4. 5+4i 2+i

Algebra and Trigonometry (6th Edition)
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ISBN:9780134463216
Author:Robert F. Blitzer
Publisher:Robert F. Blitzer
ChapterP: Prerequisites: Fundamental Concepts Of Algebra
Section: Chapter Questions
Problem 1MCCP: In Exercises 1-25, simplify the given expression or perform the indicated operation (and simplify,...
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**Complex Number Division**

**Problem 4:**

\[ \frac{5 + 4i}{2 + i} \]

In this problem, we are tasked with dividing the complex number \(5 + 4i\) by \(2 + i\). To perform this division, we multiply the numerator and the denominator by the conjugate of the denominator.

**Steps:**

1. Identify the conjugate of the denominator. The conjugate of \(2 + i\) is \(2 - i\).

2. Multiply both the numerator and the denominator by the conjugate:

   \[
   \frac{(5 + 4i)(2 - i)}{(2 + i)(2 - i)}
   \]

3. Simplify the expression. The denominator becomes a real number since:

   \[
   (2 + i)(2 - i) = 2^2 - i^2 = 4 + 1 = 5
   \]

4. Multiply out the terms in the numerator:

   \[
   (5 + 4i)(2 - i) = 5 \cdot 2 - 5 \cdot i + 4i \cdot 2 - 4i \cdot i = 10 - 5i + 8i - 4i^2
   \]

5. Simplify the expression:

   Since \(i^2 = -1\), replace \(-4i^2\) with \(4\). The expression now is:

   \[
   10 - 5i + 8i + 4 = 14 + 3i
   \]

6. Divide each term by the real number in the denominator:

   \[
   \frac{14 + 3i}{5} = \frac{14}{5} + \frac{3i}{5}
   \]

Thus, the solution to the problem is:

\[
\frac{14}{5} + \frac{3}{5}i
\]

This solution explains how to divide complex numbers using the method of multiplying by the conjugate.
Transcribed Image Text:**Complex Number Division** **Problem 4:** \[ \frac{5 + 4i}{2 + i} \] In this problem, we are tasked with dividing the complex number \(5 + 4i\) by \(2 + i\). To perform this division, we multiply the numerator and the denominator by the conjugate of the denominator. **Steps:** 1. Identify the conjugate of the denominator. The conjugate of \(2 + i\) is \(2 - i\). 2. Multiply both the numerator and the denominator by the conjugate: \[ \frac{(5 + 4i)(2 - i)}{(2 + i)(2 - i)} \] 3. Simplify the expression. The denominator becomes a real number since: \[ (2 + i)(2 - i) = 2^2 - i^2 = 4 + 1 = 5 \] 4. Multiply out the terms in the numerator: \[ (5 + 4i)(2 - i) = 5 \cdot 2 - 5 \cdot i + 4i \cdot 2 - 4i \cdot i = 10 - 5i + 8i - 4i^2 \] 5. Simplify the expression: Since \(i^2 = -1\), replace \(-4i^2\) with \(4\). The expression now is: \[ 10 - 5i + 8i + 4 = 14 + 3i \] 6. Divide each term by the real number in the denominator: \[ \frac{14 + 3i}{5} = \frac{14}{5} + \frac{3i}{5} \] Thus, the solution to the problem is: \[ \frac{14}{5} + \frac{3}{5}i \] This solution explains how to divide complex numbers using the method of multiplying by the conjugate.
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