Chapter 11: Problem 50
Multiply and simplify. $$\left(\frac{1}{3}-\frac{4}{3} i\right)\left(\frac{3}{4}+\frac{2}{3} i\right)$$
Short Answer
Expert verified
\(\left(\frac{1}{3}-\frac{4}{3}i\right)\left(\frac{3}{4}+\frac{2}{3}i\right) = \frac{41}{36} - \frac{7}{9}i\)
Step by step solution
01
Identify the complex numbers
We are given two complex numbers in the form of a fraction:
\(A = \frac{1}{3}-\frac{4}{3}i\) and \(B = \frac{3}{4}+\frac{2}{3}i\)
02
Multiply the complex numbers
We will use the formula for multiplying complex numbers:
\((a + bi)(c + di) = (ac - bd) + (ad + bc)i\)
Using this formula, we will multiply A and B:
\((\frac{1}{3}-\frac{4}{3}i)(\frac{3}{4}+\frac{2}{3}i) = \left(\frac{1}{3}\cdot\frac{3}{4}-(-\frac{4}{3}\cdot\frac{2}{3})\right) + \left(\frac{1}{3}\cdot\frac{2}{3} + (-\frac{4}{3}\cdot\frac{3}{4})\right)i\)
03
Calculate and simplify the result
Now, we will simplify the real and imaginary parts of the result:
Real part: \(\frac{1}{3}\cdot\frac{3}{4} + \frac{4}{3}\cdot\frac{2}{3} = \frac{1}{4} + \frac{8}{9}\)
Imaginary part: \(\frac{1}{3}\cdot\frac{2}{3} - \frac{4}{3}\cdot\frac{3}{4} = \frac{2}{9} - 1\)
Now, let's find the common denominator and add the terms in the real part:
\(\frac{1}{4} + \frac{8}{9} = \frac{9}{36} + \frac{32}{36} = \frac{41}{36}\)
In the imaginary part, the common denominator is already present, so we can directly subtract the terms:
\(\frac{2}{9} - 1 = \frac{2}{9} - \frac{9}{9} = -\frac{7}{9}\)
04
Write the final answer
Combine the simplified real and imaginary parts to get the final answer:
\(\left(\frac{1}{3}-\frac{4}{3}i\right)\left(\frac{3}{4}+\frac{2}{3}i\right) = \frac{41}{36} - \frac{7}{9}i\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Imaginary Unit
The imaginary unit, denoted as \(i\), is a fundamental concept when dealing with complex numbers. It is defined as the square root of -1, implying that \(i^2 = -1\). This special property provides a way to extend the real number system to include solutions to equations that don't have real solutions, such as \(x^2 + 1 = 0\).
When multiplying complex numbers, it's essential to handle the powers of \(i\) correctly.
It's a stepping stone for handling and operating on complex numbers smoothly.
When multiplying complex numbers, it's essential to handle the powers of \(i\) correctly.
- \(i^2\) results in -1, affecting how terms in complex number expressions simplify.
- When multiplying expressions that include \(i\), keep track of these powers to simplify properly.
It's a stepping stone for handling and operating on complex numbers smoothly.
Complex Number Simplification
Simplification of complex numbers includes organizing both the real and imaginary parts into a clearer, most reduced form. A complex number is typically expressed as \(a + bi\), where \(a\) represents the real part and \(b\) is the coefficient of the imaginary part.
In multiplication, like our given expression \((\frac{1}{3} - \frac{4}{3}i)(\frac{3}{4} + \frac{2}{3}i)\), we must apply the distributive property, often referred to as 'FOIL' for two binomials:
In multiplication, like our given expression \((\frac{1}{3} - \frac{4}{3}i)(\frac{3}{4} + \frac{2}{3}i)\), we must apply the distributive property, often referred to as 'FOIL' for two binomials:
- First: Multiply the first terms in the binomial expressions.
- Outside: Multiply the outer terms.
- Inside: Multiply the inner terms.
- Last: Multiply the last terms.
- Combine like terms (real and imaginary separately).
- Apply \(i^2 = -1\) where necessary to rewrite imaginary parts correctly.
Multiplying Fractions
When multiplying fractions, the process is straightforward and is an essential skill for simplifying expressions with complex numbers. The multiplication involves:
Be mindful of common denominators when adding or subtracting the resulting fractions. To combine fractions properly:
- Multiplying the numerators to get the new numerator.
- Multiplying the denominators to get the new denominator.
Be mindful of common denominators when adding or subtracting the resulting fractions. To combine fractions properly:
- Find a common denominator if you need to add or subtract fractions.
- Convert the fractions accordingly.
- Perform the addition or subtraction.