Ch. 4 - Exponential and Logarithmic Functions

Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook

Blitzer 8th Edition

Ch. 4 - Exponential and Logarithmic Functions

Problem 53

Chapter 5, Problem 53

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. log₄(x+5)=3

Verified step by step guidance

Identify the given logarithmic equation: $\log_{4}(x+5) = 3$.

Recall the definition of logarithm: $\log_{a}(b) = c$ means $a^{c} = b$. Apply this to rewrite the equation as $4^{3} = x + 5$.

Calculate the value of \$4^{3}$ (but do not finalize the numeric value here), so the equation becomes $x + 5 = 4^{3}$.

Isolate $x$ by subtracting 5 from both sides: $x = 4^{3} - 5$.

Check the domain restriction: since the argument of the logarithm $x + 5$ must be greater than 0, ensure that $x + 5 > 0$, which means $x > -5$. Confirm that your solution satisfies this domain condition.

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Key Concepts

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

Definition and Properties of Logarithms

A logarithm log_b(a) answers the question: to what power must the base b be raised to get a? Understanding this definition allows you to rewrite logarithmic equations in exponential form, which is essential for solving equations like log_4(x+5) = 3.

Domain of Logarithmic Functions

The domain of a logarithmic function log_b(f(x)) requires that the argument f(x) be positive. This means x+5 > 0 in the given problem, so x must be greater than -5. Checking the domain ensures that any solution found is valid within the original equation.

Converting Logarithmic Equations to Exponential Form

To solve log_b(f(x)) = c, rewrite it as f(x) = b^c. For log_4(x+5) = 3, this becomes x+5 = 4^3. This conversion simplifies the problem to solving an algebraic equation, making it easier to find the exact value of x.

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Related Practice

Textbook Question

Begin by graphing f(x) = log₂ x. Then use transformations of this graph to graph the given function. What is the vertical asymptote? Use the graphs to determine each function's domain and range. g(x) = log₂ (x + 1)

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Textbook Question

Use the compound interest formulas A = P (1+ r/n)^nt and A =Pe^rt to solve exercises 53-56. Round answers to the nearest cent. Find the accumulated value of an investment of \$10,000 for 5 years at an interest rate of 1.32% if the money is b. compounded quarterly

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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. 2 log_b x + 3 log_b y

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. $\ln \sqrt[3]{\frac{x}{e}}$

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