Chapter 8: Problem 62
For Exercises 49-64, write each quotient in standard form. $$ \frac{7+4 i}{9-3 i} $$
Short Answer
Expert verified
The quotient in standard form is \( \frac{17}{30} + \frac{19}{30}i \).
Step by step solution
01
Write the Original Expression
The given expression is \( \frac{7+4i}{9-3i} \). Our goal is to write this quotient in standard form, which is \( a + bi \), where \( a \) and \( b \) are real numbers.
02
Multiply by the Conjugate
To eliminate the imaginary unit \( i \) from the denominator, multiply both the numerator and denominator by the conjugate of the denominator. The conjugate of \( 9-3i \) is \( 9+3i \).Perform the multiplication:\[ \frac{(7+4i)(9+3i)}{(9-3i)(9+3i)} \]
03
Simplify the Denominator
Simplify the denominator using the difference of squares formula, \( a^2 - b^2 \):\[ (9)^2 - (3i)^2 = 81 - 9(-1) = 81 + 9 = 90 \]
04
Expand the Numerator
Expand the expression \((7+4i)(9+3i)\) using distributive property:\[ 7 \cdot 9 + 7 \cdot 3i + 4i \cdot 9 + 4i \cdot 3i \= 63 + 21i + 36i + 12i^2 \= 63 + 57i + 12(-1) = 63 + 57i - 12 = 51 + 57i \]
05
Divide Real and Imaginary Components
Now, separate the real part and the imaginary part of the result:The expression becomes \( \frac{51 + 57i}{90} \).This can be written as: \\( \frac{51}{90} + \frac{57}{90}i \).
06
Simplify Each Component
Simplify each part: \( \frac{51}{90} = \frac{17}{30} \) and \( \frac{57}{90} = \frac{19}{30} \).Thus, the expression in standard form is \( \frac{17}{30} + \frac{19}{30}i \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Standard Form
When dealing with complex numbers, the standard form is a way of expressing them with both real and imaginary parts clearly separated. A complex number in standard form looks like this:
- The formula: \( a + bi \)
- Where \( a \) represents the real part of the number.
- And \( b \) is the coefficient of the imaginary part (with the imaginary unit denoted as \( i \)).
Conjugate
The conjugate of a complex number is essential in simplifying expressions that have imaginary components. If you have a complex number such as \( a + bi \), its conjugate is \( a - bi \). By changing the sign of the imaginary part, we use the conjugate to eliminate the imaginary unit from the denominator of a fraction. When you multiply a number by its conjugate, it results in a real number. This outcome is because:
- The product \( (a + bi)(a - bi) \) uses the formula \( a^2 - b^2i^2 \).
- Since \( i^2 = -1 \), the expression simplifies to \( a^2 + b^2 \).
Imaginary Unit
Imaginary numbers revolve around the imaginary unit, denoted as \( i \). The defining property of the imaginary unit is that \( i^2 = -1 \). This property allows you to work with numbers that involve square roots of negative values. In practical terms:
- Any complex number can be expressed in terms of \( i \), as in the form \( a + bi \).
- Operations including multiplication, division, and addition with complex numbers are handled using this unit.
- While real numbers appear along the real number line, complex numbers occupy a plane needing both real and imaginary axes.
Real and Imaginary Components
A complex number is made up of two parts: the real part and the imaginary part.
- The real part is denoted by \( a \) and is a component that does not involve \( i \).
- The imaginary component is denoted by \( b \), involved with the unit \( i \).
- You start by separating real and imaginary parts after eliminating \( i \) from the denominator.
- The result can be simplified, giving each part its own distinct expression.
- This leads to a clear standard form, such as \( \frac{17}{30} + \frac{19}{30}i \) seen in the exercise solution.