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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 69

The figure shows the graph of f(x) = ln x. In Exercises 65–74, use transformations of this graph to graph each function. Graph and give equations of the asymptotes. Use the graphs to determine each function's domain and range. g(x) = 2 ln x

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Recall the parent function: \(f(x) = \ln x\), which has a vertical asymptote at \(x = 0\), domain \((0, \infty)\), and range \((-\infty, \infty)\).
Identify the transformation in \(g(x) = 2 \ln x\): the factor 2 is a vertical stretch by a factor of 2, which stretches the graph of \(\ln x\) vertically but does not affect the domain or the asymptote.
Write the equation of the asymptote for \(g(x)\): since the transformation does not shift the graph horizontally, the vertical asymptote remains at \(x = 0\).
Determine the domain of \(g(x)\): because the input to the logarithm must be positive, the domain remains \((0, \infty)\).
Determine the range of \(g(x)\): since vertical stretching does not restrict the output values of the logarithm, the range remains \((-\infty, \infty)\).

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Key Concepts

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

Logarithmic Functions and Their Graphs

A logarithmic function, such as f(x) = ln x, is the inverse of an exponential function. Its graph passes through (1,0) and is defined only for x > 0. Understanding the shape and behavior of the natural logarithm graph is essential for applying transformations.
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Graphs of Logarithmic Functions

Transformations of Functions

Transformations include vertical stretches, compressions, shifts, and reflections applied to a base graph. For g(x) = 2 ln x, the factor 2 vertically stretches the graph of ln x by a factor of 2, affecting the steepness but not the domain or asymptote location.
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Domain & Range of Transformed Functions

Asymptotes, Domain, and Range of Logarithmic Functions

The vertical asymptote of ln x is the y-axis (x=0), where the function is undefined. The domain of ln x and its transformations is x > 0, while the range is all real numbers. Recognizing how transformations affect these properties is key to graphing and describing the function.
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Graphs of Logarithmic Functions
Related Practice
Textbook Question

In Exercises 71–78, use common logarithms or natural logarithms and a calculator to evaluate to four decimal places. log5 13

Textbook Question

In Exercises 64–73, solve each exponential equation. Where necessary, express the solution set in terms of natural or common logarithms and use a calculator to obtain a decimal approximation, correct to two decimal places, for the solution. 8x=121438^x = 12143

Textbook Question

The figure shows the graph of f(x) = ln x. In Exercises 65–74, use transformations of this graph to graph each function. Graph and give equations of the asymptotes. Use the graphs to determine each function's domain and range.

h(x) = ln (2x)

Textbook Question

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. log3(x+6)+log3(x+4)=1

Textbook Question

The figure shows the graph of f(x) = ln x. In Exercises 65–74, use transformations of this graph to graph each function. Graph and give equations of the asymptotes. Use the graphs to determine each function's domain and range. h(x) = ln(x/2)

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. logx+log(x21)log7log(x+1)\(\log\) x + \(\log\)(x^2 - 1) - \(\log\) 7 - \(\log\)(x + 1)