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In Exercises 13-40, perform the indicated operation, simplify, and express in standard form. $$ \left(\frac{1}{2}+2 i\right)\left(\frac{4}{9}-3 i\right) $$

Short Answer

Expert verified
The standard form is \( \frac{56}{9} - \frac{11}{18}i \).

Step by step solution

01

Distribute each term in the first expression

To multiply the two complex numbers \( \left(\frac{1}{2}+2i\right)\left(\frac{4}{9}-3i\right) \), we start by distributing each term in \( \left(\frac{1}{2}+2i\right)\) across \( \left(\frac{4}{9}-3i\right)\). This means we will calculate four separate products: 1. \( \frac{1}{2} \cdot \frac{4}{9} \)2. \( \frac{1}{2} \cdot (-3i) \)3. \( 2i \cdot \frac{4}{9} \)4. \( 2i \cdot (-3i) \)
02

Calculate each product

Perform each multiplication:1. \( \frac{1}{2} \cdot \frac{4}{9} = \frac{4}{18} = \frac{2}{9} \)2. \( \frac{1}{2} \cdot (-3i) = -\frac{3}{2}i \)3. \( 2i \cdot \frac{4}{9} = \frac{8}{9}i \)4. \( 2i \cdot (-3i) = -6i^2 = 6 \) (since \( i^2 = -1\))
03

Combine real and imaginary parts

Now sum up all the real and imaginary parts from the previous step:- Real parts: \( \frac{2}{9} + 6 = \frac{2}{9} + \frac{54}{9} = \frac{56}{9} \)- Imaginary parts: \( -\frac{3}{2}i + \frac{8}{9}i \) Convert \( -\frac{3}{2}i \) to a common denominator: \( -\frac{3}{2}i = -\frac{27}{18}i \), and \( \frac{8}{9}i = \frac{16}{18}i \) Combine: \( -\frac{27}{18}i + \frac{16}{18}i = -\frac{11}{18}i \)
04

Write in standard form

Combine the results to express the complex number in standard form, which is \( a + bi \):\[ \frac{56}{9} - \frac{11}{18}i \]

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Distributive Property
When working with complex numbers, leveraging the distributive property is key in simplifying expressions. Think of the distributive property as a way to multiply each term in one set of parentheses by each term in another set. This is much like distributing goods from a warehouse to different stores. For example, when we apply it to \( \left(\frac{1}{2} + 2i\right)\left(\frac{4}{9} - 3i\right)\), we distribute \(\frac{1}{2}\) to both \(\frac{4}{9}\) and \(-3i\), and do the same with \( 2i \).
  • First Distribution: \( \frac{1}{2} \times \frac{4}{9} \) and \( \frac{1}{2} \times -3i \)
  • Second Distribution: \( 2i \times \frac{4}{9} \) and \( 2i \times -3i \)
Notice how we break it down into smaller pieces. Each of these products is calculated separately and later combined. The distributive property helps in systematically breaking down complex multiplications, making it easier to handle each part step by step.
Real and Imaginary Parts
In any complex number, there are two main components: the real part and the imaginary part. This is the beauty of complex numbers, as it allows calculations beyond the real plane by incorporating the 'imaginary' unit, denoted as \(i\), where \(i^2 = -1\). When we simplify a product of two complex numbers, we need to separately collect and add together the real and imaginary parts to maintain this structure.
Consider the expression after distributing:
  • Real parts: \( \frac{2}{9} + 6 \) combined to \(\frac{56}{9}\)
  • Imaginary parts: \( -\frac{3}{2}i + \frac{8}{9}i \) combined to \(-\frac{11}{18}i\)
This practice of separating and then combining the real and imaginary components reinforces the integrity of the complex number, keeping it in its standard form \( a + bi \), where \(a\) is the real part, and \(bi\) is the imaginary part.
Multiplication of Fractions
When dealing with complex numbers, multiplication often involves handling fractions, especially when each component is a fraction, as seen in our example: \( \frac{1}{2} \times \frac{4}{9} \).
Multiplying fractions is usually straightforward: multiply the numerators together and then the denominators. For instance,
  • \( \frac{1}{2} \times \frac{4}{9} = \frac{1 \times 4}{2 \times 9} = \frac{4}{18} = \frac{2}{9} \)
In more complex calculations involving \(i\), such as\(2i \times -3i\), remember that \(i^2 = -1\).
  • Thus, \(2i \times -3i = -6i^2 = 6\).
Understanding how to multiply fractions effectively makes tackling complex multiplications manageable. It is crucial to simplify fractions at the end to get the final result in its simplest form, ensuring clarity and correctness.

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