Chapter 10: Problem 37
Write each quotient in the form \(a+b i\) $$ \frac{3+5 i}{1+i} $$
Short Answer
Expert verified
The quotient in the form \( a + bi \) is \( 4 + i \).
Step by step solution
01
Represent the Quotient
The given complex quotient is \( \frac{3+5i}{1+i} \). We need to write it in the form \( a + bi \).
02
Multiply by the Conjugate
Multiply both the numerator and the denominator by the conjugate of the denominator. The conjugate of \( 1+i \) is \( 1-i \). So, multiply by \( \frac{1-i}{1-i} \):\[\frac{(3+5i)(1-i)}{(1+i)(1-i)}\]
03
Simplify the Denominator
Calculate \( (1+i)(1-i) \) which is a difference of squares: \[ (1+i)(1-i) = 1^2 - (i)^2 = 1 - (-1) = 2 \] The denominator simplifies to 2.
04
Expand the Numerator
Distribute \( 3+5i \) and \( 1-i \) in the numerator: \[(3+5i)(1-i) = 3\cdot1 + 3\cdot(-i) + 5i\cdot1 + 5i\cdot(-i) = 3 - 3i + 5i - 5i^2\] Since \( i^2 = -1 \), it becomes:\[3 - 3i + 5i + 5 = 8 + 2i\] The expanded numerator is \( 8 + 2i \).
05
Write in the Form \( a + bi \)
Combine the results of the numerator and the denominator:\[\frac{8+2i}{2} = \frac{8}{2} + \frac{2i}{2} = 4 + i\] This is the quotient in the form \( a + bi \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Complex Conjugate
In the realm of complex numbers, the complex conjugate of a given complex number is obtained by changing the sign of its imaginary part. For instance, the complex conjugate of \( 1 + i \) is \( 1 - i \). Conjugates are instrumental in simplifying complex fractions. When you multiply a complex number by its conjugate, the imaginary parts cancel out to give a real number. This technique is essential for dividing complex numbers because it eliminates the imaginary unit from the denominator, resulting in a simpler form \( a + bi \). So, anytime you see a quotient of complex numbers, think about using the conjugate for simplification.
Imaginary Unit
The imaginary unit, denoted as \( i \), is a fundamental building block of complex numbers. It is defined as the square root of \(-1\), which means \( i^2 = -1 \). This unique property allows imaginary numbers to stretch the number system beyond the real numbers. When working with complex numbers, keep in mind this characteristic of \( i \) because it crucially influences calculations, like when expanding expressions or simplifying products. Just remember, if ever you square \( i \), you get \(-1\), and this plays a key role in many aspects of complex number manipulation.
Difference of Squares
The concept of difference of squares is a powerful algebraic tool that simplifies expressions involving squares. In the case of complex numbers, the product \((1+i)(1-i)\) results in a difference of squares. This is because it follows the form \( a^2 - b^2 \), where \( a = 1 \) and \( b = i \). When you multiply, you get:
- \( 1^2 = 1 \)
- \( (i)^2 = -1 \)
Multiplying Complex Numbers
Multiplying complex numbers follows the distributive property, just like multiplication of polynomials. Consider the expression \((3 + 5i)(1 - i)\). Start by expanding:
- \(3 \cdot 1 = 3\)
- \(3 \cdot (-i) = -3i\)
- \(5i \cdot 1 = 5i\)
- \(5i \cdot (-i) = -5i^2\)