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Ch. 4 - Exponential and Logarithmic Functions
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 5, Problem 49

Solve each logarithmic equation in Exercises 49–92. Be sure to reject any value of x that is not in the domain of the original logarithmic expressions. Give the exact answer. Then, where necessary, use a calculator to obtain a decimal approximation, correct to two decimal places, for the solution. log3x=4

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Identify the given logarithmic equation: \(\log_{3} x = 4\).
Recall the definition of a logarithm: \(\log_{a} b = c\) means \(a^{c} = b\). Using this, rewrite the equation as \(3^{4} = x\).
Calculate the value of \$3^{4}\( to find \)x$. (You can leave it as an expression for the exact answer.)
Check the domain of the original logarithmic expression. Since \(\log_{3} x\) is defined only for \(x > 0\), ensure your solution satisfies this condition.
If needed, use a calculator to find the decimal approximation of \(x\) to two decimal places.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Definition of Logarithms

A logarithm answers the question: to what exponent must the base be raised to produce a given number? For example, log₃(x) = 4 means 3 raised to the power 4 equals x. Understanding this definition allows you to rewrite logarithmic equations in exponential form to solve for the variable.
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Domain of Logarithmic Functions

The domain of a logarithmic function log_b(x) includes only positive real numbers (x > 0) because logarithms of zero or negative numbers are undefined. When solving logarithmic equations, it is essential to check that solutions fall within this domain to ensure they are valid.
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Exact and Approximate Solutions

Logarithmic equations often yield exact solutions expressed in exponential form. However, when a decimal approximation is required, a calculator can be used to find a numerical value, typically rounded to a specified number of decimal places, such as two decimals for clarity and precision.
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Related Practice
Textbook Question

Graph functions f and g in the same rectangular coordinate system. Graph and give equations of all asymptotes. If applicable, use a graphing utility to confirm your hand-drawn graphs. f(x) = 3x and g(x) = 3-x

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Textbook Question

Solve each exponential equation in Exercises 23–48. Express the solution set in terms of natural logarithms or common logarithms. Then use a calculator to obtain a decimal approximation, correct to two decimal places, for the solution. 32x+3x−2=0

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Textbook Question

Use properties of logarithms to condense each logarithmic expression. Write the expression as a single logarithm whose coefficient is 1. Where possible, evaluate logarithmic expressions without using a calculator. log x + 3 log y

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Textbook Question

Graph functions f and g in the same rectangular coordinate system. Graph and give equations of all asymptotes. If applicable, use a graphing utility to confirm your hand-drawn graphs. f(x) = 3x and g(x) = (1/3). 3x

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Textbook Question

In Exercises 50–53, use properties of logarithms to expand each logarithmic expression as much as possible. Where possible, evaluate logarithmic expressions without using a calculator. log4(x64)\(\log\)_4\(\left\)(\(\frac{\sqrt{x}\)}{64}\(\right\))

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Textbook Question

Use properties of logarithms to condense each logarithmic expression. Write the expression as a single logarithm whose coefficient is 1. Where possible, evaluate logarithmic expressions without using a calculator. (1/2)ln x + ln y

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