/*! 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 18 Evaluate the logarithm using the... [FREE SOLUTION] | 91Ó°ÊÓ

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Evaluate the logarithm using the change-of-base formula. Round your result to three decimal places. $$\log _{1 / 4} 5$$

Short Answer

Expert verified
The result will represent the solution for the original logarithm \( \log_{1/4} 5 \) to three decimal places. Its exact value depends on the specific values returned by the calculator or logarithm table when evaluating \( \log {5} \) and \( \log {(1/4)} \) to three decimal places.

Step by step solution

01

Identify Values Using Change-of-Base Formula

The log to be evaluated is \( \log_{1/4} 5 \). Based on the change-of-base formula \( \log_b a = \frac{\log c}{\log d} \), we can identify \( a = 5, b = 1/4 \). We then rewrite the logarithm, replacing the base \( b \) of the logarithm with base 10. The base 10 is usually used because it is the most common logarithmic base.
02

Application of Change-of-Base Formula

Rewrite \( \log_{1/4} 5 \) as \( \frac{\log {5}}{\log {(1/4)}} \). This results from application of the change-of-base formula discussed in Step 1.
03

Evaluation of Logarithmic Expressions

Evaluate both \( \log {5} \) and \( \log {(1/4)} \). Using a calculator or logarithm table, find these values to three decimal places.
04

Calculation of Final Answer

Divide the result from evaluating \( \log {5} \) by the result from evaluating \( \log {(1/4)} \) to get the final answer.

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Key Concepts

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

Logarithm Evaluation
Understanding how to evaluate logarithms is essential in mathematics. A logarithm answers the question: to what power must we raise a base number to obtain a certain value? In terms of notation, the logarithm of a number with a given base is written as \( \log_{base} (number) \). For instance, if you have \( \log_{1/4} 5 \) it means you're trying to find out the power to which \(1/4\) must be raised to get \(5\).

To evaluate logarithms without a common base, we frequently use the change-of-base formula. This formula allows us to convert a logarithm with a base that is not easily handled to one with a base of 10, which we can easily find using a calculator. For instance, \( \log_{1/4} 5 \) can be expressed as \( \frac{\log 5}{\log 1/4} \) using base 10. It's imperative to remember the rounding rule; as the final answer often requires a specific number of decimal places, rounding to three decimal places is common practice in many mathematical problems.
Logarithmic Expressions
When dealing with logarithmic expressions, it's important to recognize their unique properties and how they differ from other mathematical operations. Logarithmic expressions involve the logarithm function, which is the inverse of exponential functions. These expressions show up in various equations, and it's crucial to understand how to manipulate and evaluate them.

To simplify a logarithmic expression, you can use several techniques. The change-of-base formula is a powerful tool which lets you convert logarithms of awkward bases into more calculable forms, usually with a base of 10 or the natural logarithm base e. For example, \( \log_{1/4} 5 \) might look formidable at first, but with the change-of-base formula, it can be rewritten based on the properties of logarithms to \( \frac{\log 5}{\log 1/4} \), where both logarithms are using base 10, which is far more manageable using a standard calculator.
Mathematical Problem-Solving
Mathematical problem-solving requires a systematic approach to uncover the solution to a particular challenge. When faced with a logarithmic problem like \( \log_{1/4} 5 \) using the change-of-base formula, it involves several phases: comprehension, transformation, calculation, and review.

Initially, you must understand the problem – what is being asked, and which tools or formulas can be applied. Then, transform the original expression by applying those tools. In this case, the change-of-base formula allows us to rewrite the expression into a more familiar form. Consecutively, the calculation phase involves carrying out necessary operations, such as division or multiplication, to arrive at the numerical answer. Finally, the review phase requires you verify your answer for correctness and adherence to any specific instructions, like rounding off to three decimal places. By breaking down a problem into these categories, you can navigate through complex mathematical tasks in a structured and less daunting way.

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Most popular questions from this chapter

A cup of water at an initial temperature of \(78^{\circ} \mathrm{C}\) is placed in a room at a constant temperature of \(21^{\circ} \mathrm{C}\). The temperature of the water is measured every 5 minutes during a half-hour period. The results are recorded as ordered pairs of the form \((t, T),\) where \(t\) is the time (in minutes) and \(T\) is the temperature (in degrees Celsius). \(\left(0,78.0^{\circ}\right),\left(5,66.0^{\circ}\right),\left(10,57.5^{\circ}\right),\left(15,51.2^{\circ}\right)\) \(\left(20,46.3^{\circ}\right),\left(25,42.4^{\circ}\right),\left(30,39.6^{\circ}\right)\) (a) The graph of the model for the data should be asymptotic with the graph of the temperature of the room. Subtract the room temperature from each of the temperatures in the ordered pairs. Use a graphing utility to plot the data points \((t, T)\) and \((t, T-21)\). (b) An exponential model for the data \((t, T-21)\) is given by \(T-21=54.4(0.964)^{t} .\) Solve for \(T\) and graph the model. Compare the result with the plot of the original data. (c) Take the natural logarithms of the revised temperatures. Use a graphing utility to plot the points \((t, \ln (T-21))\) and observe that the points appear to be linear. Use the regression feature of the graphing utility to fit a line to these data. This resulting line has the form \(\ln (T-21)=a t+b\). Solve for \(T,\) and verify that the result is equivalent to the model in part (b). (d) Fit a rational model to the data. Take the reciprocals of the \(y\) -coordinates of the revised data points to generate the points \(\left(t, \frac{1}{T-21}\right)\) Use a graphing utility to graph these points and observe that they appear to be linear. Use the regression feature of a graphing utility to fit a line to these data. The resulting line has the form \(\frac{1}{T-21}=a t+b\) Solve for \(T,\) and use a graphing utility to graph the rational function and the original data points. (e) Why did taking the logarithms of the temperatures lead to a linear scatter plot? Why did taking the reciprocals of the temperatures lead to a linear scatter plot?

Four-legged animals run with two different types of motion: trotting and galloping. An animal that is trotting has at least one foot on the ground at all times, whereas an animal that is galloping has all four feet off the ground at some point in its stride. The number of strides per minute at which an animal breaks from a trot to a gallop depends on the weight of the animal. Use the table to find a logarithmic equation that relates an animal's weight \(x\) (in pounds) and its lowest galloping speed \(y\) (in strides per minute). $$ \begin{array}{|c|c|} \hline \text { Weight, } x & \text { Galloping speed, } y \\ \hline 25 & 191.5 \\ 35 & 182.7 \\ 50 & 173.8 \\ 75 & 164.2 \\ 500 & 125.9 \\ 1000 & 114.2 \\ \hline \end{array} $$

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