Chapter 8: Problem 47
Find the following products. \((3+2 i)^{2}\)
Short Answer
Expert verified
The product is \(5 + 12i\).
Step by step solution
01
Identify the Expression Form
Recognize that the expression provided is \((3 + 2i)^{2}\). This is a complex number raised to the power of 2.
02
Apply Binomial Theorem
Use the binomial theorem for the square of a binomial. In general, \((a + b)^{2} = a^{2} + 2ab + b^{2}\). Here, let \(a = 3\) and \(b = 2i\).
03
Calculate Each Part Separately
First calculate \(a^{2}\):\((3)^{2} = 9\).Then \(2ab\):\(2 \cdot 3 \cdot 2i = 12i\).Finally, calculate \(b^{2}\):\((2i)^{2} = 4i^{2} = 4(-1) = -4\).
04
Sum the Results
Combine all calculated parts:\(a^{2} + 2ab + b^{2} = 9 + 12i - 4\). Simplify by combining like terms:\(5 + 12i\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Binomial Theorem
The binomial theorem provides a way to expand expressions that are raised to a power. It is used frequently in algebra to expand binomials. This theorem states:
- For any binomial expression of the form o(a + b)^{n}= \sum_{k=0}^{n} \binom{n}{k}a^{n-k}b^{k}.
- For our specific exercise with o(a + b)^{2}, we use a simplified version: o(a + b)^{2} = a^{2} + 2ab + b^{2}.
- Here, the terms of the expansion represent different parts: a^{2} yields the square of the first term, \(2ab\) accounts for two times the product of both terms, and b^{2} gives the square of the second term.
Imaginary Unit
The imaginary unit, denoted as \(i\), is a mathematical concept used to handle numbers that involve the square root of negative one. Normally, taking the square root of a negative number isn’t possible with real numbers. But with complex numbers, it becomes feasible using \(i\). Here's more about this pivotal concept:
- Imaginary unit \(i\) is defined as \(i = \sqrt{-1}\) which implies \(i^{2} = -1\).
- It allows extension of the real number system to include complex numbers, which have the form \(a + bi\).
- In our exercise, when we calculate \((2i)^{2}\), it's vital to remember \(i^{2} = -1\) so \((2i)^{2} = 4i^{2} = 4(-1) = -4\).
Complex Multiplication
Complex multiplication involves multiplying two complex numbers, taking both the real and imaginary parts into account. Here's how to handle it:
- Consider two complex numbers: \((a + bi)\) and \((c + di)\).
- The product of these would be: \((a + bi)(c + di) = ac + adi + bci + bdi^{2}\).
- Contribute each part: multiply the real parts to get one component, real and imaginary parts for another, consider \(i^{2}=-1\) for another.
- Sum up these separate products, simplifying based on properties of \(i\).
- In our example, \((3+2i)^{2}\) represents a self-product of a complex number; applying simplified binomial logic helps find \(5 + 12i\) as combined parts.