Chapter 9: Problem 26
Write each as a logarithmic equation. See Example 2. $$ 3^{-4}=\frac{1}{81} $$
Short Answer
Expert verified
\( \log_3\left(\frac{1}{81}\right) = -4 \)
Step by step solution
01
Understand the Exponential Equation
The given equation is an exponential equation where the base is 3, the exponent is -4, and the result is \( \frac{1}{81} \). This can be written as \( 3^{-4} = \frac{1}{81} \).
02
Identify the Base, Exponent, and Result
In the equation \( 3^{-4} = \frac{1}{81} \), the base is 3, the exponent is -4, and the result is \( \frac{1}{81} \).
03
Recall the Definition of a Logarithm
A logarithm is the inverse of an exponentiation and answers the question: "To what exponent must the base be raised, to produce a given number?"
04
Convert the Exponential to Logarithmic Form
Using the definition of a logarithm, the equation \( 3^{-4} = \frac{1}{81} \) can be rewritten in logarithmic form as \( \log_3\left(\frac{1}{81}\right) = -4 \). This means that 3 raised to the power of -4 gives \( \frac{1}{81} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Exponential Equations
Exponential equations feature prominently when dealing with exponential functions. These involve a base being raised to a particular power, or exponent. This type of mathematical expression directly relates to concepts of growth and decay, which are found in many real-world situations. For instance, when evaluating an equation like \( 3^{-4} = \frac{1}{81} \), the base is 3 and the exponent is -4.
The essence of such equations is the relationship between the base and the power, which determines the result. Exponents can be positive, negative, or even fractional. A negative exponent, such as -4, indicates that you should take the reciprocal of the base raised to the absolute value of the exponent:\[ a^{-n} = \frac{1}{a^{n}} \]
This principle helps in understanding how \( 3^{-4} = \frac{1}{81} \) operates, as it implies that \( \frac{1}{3^4} = \frac{1}{81} \).
It is important to recognize patterns in exponential equations because they form the basis for logarithmic conversions, which are useful in solving various mathematical and real-life problems.
The essence of such equations is the relationship between the base and the power, which determines the result. Exponents can be positive, negative, or even fractional. A negative exponent, such as -4, indicates that you should take the reciprocal of the base raised to the absolute value of the exponent:\[ a^{-n} = \frac{1}{a^{n}} \]
This principle helps in understanding how \( 3^{-4} = \frac{1}{81} \) operates, as it implies that \( \frac{1}{3^4} = \frac{1}{81} \).
It is important to recognize patterns in exponential equations because they form the basis for logarithmic conversions, which are useful in solving various mathematical and real-life problems.
The Role of Logarithms
Logarithms play a crucial role as they serve as the inverse operations to exponents, providing a means to unravel exponential equations. This reverse mapping is powerful because it translates multiplication into addition, which is often easier to work with. The fundamental question a logarithm answers is: "To what exponent must a base be raised to reach a certain number?"
Consider \( 3^{-4} = \frac{1}{81} \). This equation can be converted into its logarithmic form \( \log_3\left(\frac{1}{81}\right) = -4 \). This tells us that raising 3 to -4 results in \( \frac{1}{81} \).
### Key Sub-Concepts of Logarithms:
Consider \( 3^{-4} = \frac{1}{81} \). This equation can be converted into its logarithmic form \( \log_3\left(\frac{1}{81}\right) = -4 \). This tells us that raising 3 to -4 results in \( \frac{1}{81} \).
### Key Sub-Concepts of Logarithms:
- Base: The number you raise to a power to get another number (base of 3 in this instance).
- Argument: The number for which you want to find the power (\( \frac{1}{81} \) here).
- Logarithmic Value: The exponent you reach (which is -4 in this case).
Inverse Operations in Mathematics
Inverse operations are a fundamental concept in mathematics, allowing us to reverse processes or operations. Understanding inverse operations includes recognizing how certain functions can be reversed or undone. This concept provides a foundation for solving equations, as it lets us simplify or solve for unknowns.
For instance, addition and subtraction are inverses of each other; similarly, multiplication and division are inverse operations. When it comes to exponential and logarithmic functions, the inverse relationship is crucial. Exponentiation (raising a base to a power) can be undone with a logarithm, as shown in \( 3^{-4} = \frac{1}{81} \) and \( \log_3\left(\frac{1}{81}\right) = -4 \).
### Applications and Benefits of Inverse Operations:
For instance, addition and subtraction are inverses of each other; similarly, multiplication and division are inverse operations. When it comes to exponential and logarithmic functions, the inverse relationship is crucial. Exponentiation (raising a base to a power) can be undone with a logarithm, as shown in \( 3^{-4} = \frac{1}{81} \) and \( \log_3\left(\frac{1}{81}\right) = -4 \).
### Applications and Benefits of Inverse Operations:
- Simplification: Breaking down complex problems into manageable parts by reversing processes.
- Problem Solving: Essential for solving equations where transformations need reversing.
- Theoretical Understanding: Provides insight into the deeper structure of mathematical theories and other fields.