Problem 89 - Algebra A Combined Function

Question

Write each expression in the form \(a+b i .\) $$ i^{3}+i^{4} $$

Step-by-Step Solution

Answer

The expression simplifies to \(1 - i\).

Step 1: Simplify the Expression

To simplify the expression, we start by recognizing that it involves powers of the imaginary unit, denoted as \( i \), where \( i = \sqrt{-1} \). First, we find that \( i^3 = i imes i^2 \). We already know \( i^2 = -1 \), so \( i^3 = i imes (-1) = -i \). Next, we find \( i^4 = (i^2)^2 = (-1)^2 = 1 \).

Step 2: Add the Simplified Terms

Now that we have simplified the terms, our expression \( i^3 + i^4 \) becomes \( -i + 1 \). According to the complex number form \( a + bi \), we can rewrite this expression as \( 1 - i \), where \( a = 1 \) and \( b = -1 \).

Key Concepts

Imaginary Unit

In the world of mathematics, we often encounter numbers that are not real. These are known as imaginary numbers, and the backbone of these numbers is the imaginary unit, denoted as \( i \). This unit is defined as \( i = \sqrt{-1} \). It opens up doors to solving equations that don't have solutions in the real number system, like \( x^2 + 1 = 0 \). Since no real number squared gives a negative result, \( i \) comes into play allowing us to express \( \pm i \) as the solutions. When we multiply \( i \) by itself, we begin to see a pattern that repeats, which brings us to the world of powers of \( i \). This not only helps us expand our number system but also allows us to perform calculations with a wider variety of numbers in engineering, physics, and many other fields.

Powers of i

The powers of the imaginary unit \( i \) follow a cyclic pattern, which simplifies expressions significantly. Understanding this pattern is crucial:

• \( i^1 = i \)
• \( i^2 = -1 \)
• \( i^3 = -i \) (because \( i \times i^2 = i \times (-1) \))
• \( i^4 = 1 \) (since \( i^2 \times i^2 = (-1) \times (-1) \))

This cycle repeats every four powers, meaning that any power of \( i \) can be simplified to one of these four results. To find a specific power \( i^n \), you simply divide \( n \) by 4 and use the remainder to determine what the power simplifies to. For instance, if you have \( i^{10} \), since 10 divided by 4 leaves a remainder of 2, \( i^{10} = i^2 = -1 \). Recognizing and applying this cyclical nature streamlines working with complex numbers significantly.

Simplifying Expressions

Simplifying expressions that involve powers of \( i \) is a key step in working with complex numbers, especially when aiming to express them in the form \( a + bi \). Let's consider the process with the expression \( i^3 + i^4 \). First, identify and simplify each component using the cycle of \( i \). For \( i^3 \), from the power cycle, we know \( i^3 = -i \). Similarly, \( i^4 = 1 \) because every fourth power of \( i \) is 1.Next, substitute these simplifications back into the expression: \[-i + 1\]This expression now takes on the form \( a + bi \), where \( a \) is the real component, and \( b \) is the coefficient of the imaginary component. Here, that means \( a = 1 \) and \( b = -1 \), giving us the final expression \( 1 - i \). Simplifying complex expressions using these methods helps clarify and work through problems efficiently, making the process seamless and effective in practice.