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Ch. 4 - Exponential and Logarithmic Functions
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514당신이 사용하는 게 아니라요?교과서 변경
5장, 문제 59

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(3x+2)=3

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Recall the definition of logarithm: if \(\log_{a}(b) = c\), then it is equivalent to the exponential form \(a^{c} = b\).
Rewrite the given equation \(\log_{4}(3x + 2) = 3\) in exponential form: \(4^{3} = 3x + 2\).
Calculate \$4^{3}$ (but do not finalize the numeric value) and set up the equation: \(64 = 3x + 2\).
Solve for \(x\) by isolating it: subtract 2 from both sides to get \(64 - 2 = 3x\), then divide both sides by 3 to find \(x = \frac{62}{3}\).
Check the domain restriction: the argument of the logarithm, \(3x + 2\), must be greater than 0. Substitute \(x = \frac{62}{3}\) to verify \(3\left(\frac{62}{3}\right) + 2 > 0\) to ensure the solution is valid.

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주요 개념

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Properties of Logarithms

Understanding the properties of logarithms, such as the definition log_b(a) = c means b^c = a, is essential. This allows you to rewrite logarithmic equations in exponential form to solve for the variable. Recognizing how to manipulate logs helps simplify and solve the given equation.
추천 영상:
5:36
Change of Base Property

Domain of Logarithmic Functions

The domain of a logarithmic function includes all values for which the argument (inside the log) is positive. For log_4(3x+2), the expression 3x+2 must be greater than zero. Identifying and applying domain restrictions ensures that solutions are valid and prevents extraneous answers.
추천 영상:
5:26
Graphs of Logarithmic Functions

Exact and Approximate Solutions

After solving the equation exactly, it is often necessary to provide a decimal approximation. Using a calculator to find decimal values correct to two decimal places helps interpret the solution practically. Distinguishing between exact and approximate answers is important in many algebra problems.
추천 영상:
4:20
Graph Hyperbolas at the Origin