Chapter 13: Problem 20
Express each as a sum, difference, or multiple of logarithms. See Example 2. $$\log _{3}\left(\frac{\sqrt[3]{y}}{7 x}\right)$$
Short Answer
Expert verified
\( \frac{1}{3}\log_3(y) - \log_3(7) - \log_3(x) \).
Step by step solution
01
Apply the Logarithm of a Quotient Rule
The logarithm of a quotient can be expressed as the difference of two logarithms. Therefore, apply the property: \( \log_b\left(\frac{M}{N}\right) = \log_b(M) - \log_b(N) \). For our problem, we have \( \log_3\left(\frac{\sqrt[3]{y}}{7x}\right) = \log_3(\sqrt[3]{y}) - \log_3(7x) \).
02
Simplify the Numerator Using the Logarithm of a Power Rule
The logarithm of a power can be written as the exponent times the logarithm of the base. Therefore, apply the property: \( \log_b(M^n) = n\cdot\log_b(M) \). In this step, use it for \( \log_3(\sqrt[3]{y}) \), i.e., \( \log_3(y^{1/3}) = \frac{1}{3}\log_3(y) \).
03
Apply the Logarithm of a Product Rule
For the term \( \log_3(7x) \), use the rule for the logarithm of a product, which states \( \log_b(MN) = \log_b(M) + \log_b(N) \). So, \( \log_3(7x) = \log_3(7) + \log_3(x) \).
04
Combine All Terms
Substitute all the simplified components back together: \( \log_3\left(\frac{\sqrt[3]{y}}{7x}\right) = \frac{1}{3}\log_3(y) - (\log_3(7) + \log_3(x)) \). This further simplifies to \( \frac{1}{3}\log_3(y) - \log_3(7) - \log_3(x) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Logarithms of a Quotient
The logarithm of a quotient simplifies to a difference of two logarithms. This is an important property in logarithmic calculations and is expressed as: \[\log_b\left(\frac{M}{N}\right) = \log_b(M) - \log_b(N)\]This rule is very useful when dealing with complex fractions inside logarithmic expressions. Let's consider the original example from the exercise: \[\log_3\left(\frac{\sqrt[3]{y}}{7 x}\right)\]By applying the quotient rule, we break it down into two logarithmic parts:
- \(\log_3(\sqrt[3]{y})\)
- \(- \log_3(7x)\)
Decoding Logarithms of a Power
When it comes to the logarithm of a power, you can use the exponent property to simplify expressions. This property states:\[\log_b(M^n) = n\cdot \log_b(M)\]This relationship allows you to take the exponent and multiply it by the logarithm of the base value. For our exercise, we applied this rule to the numerator:\[\log_3(\sqrt[3]{y}) \]Since \(\sqrt[3]{y}\) can also be written as \(y^{1/3}\), we use the power rule:
- \(\log_3(\sqrt[3]{y}) = \log_3(y^{1/3}) = \frac{1}{3}\log_3(y)\)
Breaking Down Logarithms of a Product
The logarithm of a product can be broken down into the sum of individual logarithms. This transformation is simplified as:\[\log_b(MN) = \log_b(M) + \log_b(N)\]Applying this rule helps manage expressions where multiple variables or constants multiply within the logarithmic function. In the exercise, we see its use on:\[\log_3(7x)\]By breaking the expression into separate logarithms, we obtain:
- \(\log_3(7x) = \log_3(7) + \log_3(x)\)