Chapter 1: Problem 264
For the following exercises, sketch the graph of the logarithmic function. Determine the domain, range, and vertical asymptote. $$ f(x)=3+\ln x $$
Short Answer
Expert verified
Domain: \((0, \infty)\), Range: \((-\infty, \infty)\), Vertical Asymptote: \(x=0\).
Step by step solution
01
Understanding the Function Form
The given function is \( f(x) = 3 + \ln x \). This is a transformation of the basic logarithmic function \( \ln x \). The function \( \ln x \) has a vertical asymptote at \( x = 0 \) and is only defined for \( x > 0 \). The transformation \( 3 + \ln x \) means the graph of \( \ln x \) is shifted up by 3 units.
02
Identifying the Domain
The domain of \( 3 + \ln x \) is the set of all \( x \) for which the function is defined. Since logarithmic functions are defined for positive \( x \) values, the domain of \( f(x) = 3 + \ln x \) is \( x > 0 \), or in interval notation, \((0, \infty)\).
03
Identifying the Range
Logarithmic functions typically have a range of all real numbers. The vertical shift does not affect this characteristic. Therefore, the range of \( 3 + \ln x \) remains as \( (-\infty, \infty) \).
04
Identifying the Vertical Asymptote
The vertical asymptote for a logarithmic function such as \( \ln x \) remains unchanged by vertical shifts. Hence, the vertical asymptote for \( 3 + \ln x \) is \( x = 0 \).
05
Sketching the Graph
To sketch the graph, start with the basic shape of \( \ln x \), which rises slowly and approaches the vertical asymptote at \( x = 0 \) from the right. Shift the entire graph upward by 3 units to account for the transformation \( 3 + \ln x \). Ensure to clearly mark the asymptote at \( x = 0 \) and label the axis.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding the Domain of a Logarithmic Function
The domain of a function describes all the possible input values (or x-values) for which the function is defined. For logarithmic functions like \( f(x) = \ln{x} \), they are only defined for positive values of \( x \). This is because you cannot take the logarithm of a negative number or zero in the real number system.
The given function \( f(x) = 3 + \ln{x} \) maintains this fundamental property of the logarithm. Therefore, the domain remains \( x > 0 \).
The given function \( f(x) = 3 + \ln{x} \) maintains this fundamental property of the logarithm. Therefore, the domain remains \( x > 0 \).
- In interval notation, this domain is represented as \((0, \infty)\).
- This means that any positive value can be plugged into the function, and it will yield a result.
Exploring the Range of a Logarithmic Function
The range of a function is all the possible output values or y-values that come out of the function. Logarithmic functions inherently have a wide range, stretching from \(-\infty\) to \(\infty\).
Even though our function is \( f(x) = 3 + \ln{x} \), where the graph is vertically shifted by 3 units, this does not alter the nature of its range. The vertical shift only affects the graph's position along the y-axis, not the set of outputs it can generate.
Even though our function is \( f(x) = 3 + \ln{x} \), where the graph is vertically shifted by 3 units, this does not alter the nature of its range. The vertical shift only affects the graph's position along the y-axis, not the set of outputs it can generate.
- This means the range of \( f(x) = 3 + \ln{x} \) remains as \((-\infty, \infty)\).
- The function can output practically any real number depending on the input value of \( x \).
Identifying Vertical Asymptotes in Logarithmic Functions
Vertical asymptotes in functions are vertical lines that the graph approaches but never actually touches or crosses. In logarithmic functions like \( \ln{x} \), a vertical asymptote occurs because the function is undefined at certain points.
For \( f(x) = 3 + \ln{x} \), the vertical asymptote is at \( x = 0 \). This is because logarithmic functions are not defined for zero or negative values.
For \( f(x) = 3 + \ln{x} \), the vertical asymptote is at \( x = 0 \). This is because logarithmic functions are not defined for zero or negative values.
- The line \( x = 0 \) is a visual boundary that the graph of the function will edge closer to but never meet or cross.
- This remains unchanged even when you apply vertical transformations, such as the addition of 3 in this case.