/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 56 Find the exact value of the loga... [FREE SOLUTION] | 91Ó°ÊÓ

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Find the exact value of the logarithmic expression without using a calculator.\(\log _{7} \frac{49}{343}\)

Short Answer

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Step by step solution

01

Express the fraction in the logarithmic expression as powers of 7

Firstly, express the both the numerator and denominator as powers of 7. 49 can be expressed as \(7^2\) and 343 can be expressed as \(7^3\)
02

Apply the quotient rule of logarithms

The quotient rule of logarithms states that the logarithm of a quotient is equal to the subtraction of the logarithm of the numerator by the logarithm of the denominator. That is, \(\log _{b} \frac{M}{N} = \log _{b} M - \log _{b} N\). So, \(\log _{7} \frac{7^2}{7^3} = \log _{7} 7^2 - \log _{7} 7^3\)
03

Simplify the logarithm

The rules of logarithms state that \(\log _{b} b^x = x\). So, \(\log _{7} 7^2 = 2\) and \(\log _{7} 7^3 = 3\). Therefore, \(\log _{7} 7^2 - \log _{7} 7^3 = 2 - 3\)

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Quotient Rule
The quotient rule in logarithms is a handy tool when dealing with expressions that involve division inside the logarithmic function. Imagine you have a fraction inside a logarithm, like in our original expression \(\log_{7} \frac{49}{343}\). The rule tells us that we can transform this into a subtraction problem, making it much easier to handle.

Here's how it works: the logarithm of a fraction \(\log_{b} \frac{M}{N}\) becomes \(\log_{b} M - \log_{b} N\). Simply put, you find the logarithm of the numerator and then subtract the logarithm of the denominator. This significantly simplifies the process, breaking it down into smaller, more manageable parts.

In our exercise, we applied the quotient rule to transform \(\log_{7} \frac{7^2}{7^3}\) into \(\log_{7} 7^2 - \log_{7} 7^3\). This decomposition sets the stage for the next steps in solving the expression.
Exponents
Understanding exponents is crucial when working with logarithms, as they often appear in the forms of bases and powers. An exponent tells us how many times a number, called the base, is multiplied by itself.

For instance, in our context, 49 can be expressed as \(7^2\), meaning 7 multiplied by itself once (7*7). Similarly, 343 can be expressed as \(7^3\), indicating 7 multiplied by itself twice (7*7*7). This recognition simplifies the numbers and makes it easier to apply rules of logarithms.

By expressing both parts of the fraction \(\frac{49}{343}\) as powers of the same base (7), the logarithmic expression becomes easier to simplify. We can then use the rule \(\log_{b} b^x = x\), which states that the logarithm of a base raised to a power equals the exponent itself. Applying this simplified even further, as you'll see shortly.
Simplifying Expressions
The final step in our problem is simplifying the expression after applying the rules of logarithms.

We start off with \(\log_{7} 7^2 - \log_{7} 7^3\). Based on the rule \(\log_{b} b^x = x\), each \(\log_{7} 7^x\) can be simplified to just \(x\). Hence, \(\log_{7} 7^2\) equals 2, and \(\log_{7} 7^3\) equals 3.

After simplifying, what began as a potentially daunting logarithm problem devolves into a simple subtraction: \(2 - 3\). This gives us the result of -1. Simplifying expressions in this way makes solving logarithmic problems far more approachable and less prone to errors. Always take it step by step, and leverage the properties of logarithms to break problems into smaller parts.

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Most popular questions from this chapter

The logarithm of the product of two numbers is equal to the sum of the logarithms of the numbers.

The number \(A\) of varieties of native prairie grasses per acre within a farming region is approximated by the model \(A=10.5 \cdot 10^{0.04 x}, \quad 0 \leq x \leq 24\) where \(x\) is the number of months since the farming region was plowed. Use this model to approximate the number of months since the region was plowed using a test acre for which \(A=70\)

Aged Population The table shows the projected U.S. populations \(P\) (in thousands) of people who are 85 years old or older for several years from 2010 to \(2050 . \quad\) (Source: U.S. Census Bureau)$$ \begin{array}{|c|c|} \hline \text { Year } & 85 \text { years and older } \\ \hline 2010 & 6123 \\ \hline 2015 & 6822 \\ \hline 2020 & 7269 \\ \hline 2025 & 8011 \\ \hline 2030 & 9603 \\ \hline 2035 & 12,430 \\ \hline 2040 & 15,409 \\ \hline 2045 & 18,498 \\ \hline 2050 & 20,861 \\ \hline \end{array} $$(a) Use a graphing utility to create a scatter plot of the data. Let \(t\) represent the year, with \(t=10\) corresponding to 2010 . (b) Use the regression feature of a graphing utility to find an exponential model for the data. Use the Inverse Property \(b=e^{\ln b}\) to rewrite the model as an exponential model in base \(e\). (c) Use a graphing utility to graph the exponential model in base \(e\). (d) Use the exponential model in base \(e\) to estimate the populations of people who are 85 years old or older in 2022 and in 2042 .

Motorola The sales per share \(S\) (in dollars) for Motorola from 1992 to 2005 can be approximated by the function \(S=\left\\{\begin{array}{lr}2.33-0.909 t+10.394 \ln t, & 2 \leq t \leq 10 \\ 0.6157 t^{2}-15.597 t+110.25, & 11 \leq t \leq 15\end{array}\right.\) where \(t\) represents the year, with \(t=2\) corresponding to 1992\. (Source: Motorola) (a) Use a graphing utility to graph the function. (b) Describe the change in sales per share that occurred in 2001 .

Solve the exponential equation algebraically. Approximate the result to three decimal places.\(\frac{119}{e^{6 x}-14}=7\)

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