Chapter 9: Problem 73
Graph and state the domain and the range of each function. $$ g(x)=\ln (x-1) $$
Short Answer
Expert verified
Domain: \( (1, \infty) \). Range: \( (-\infty, \infty) \).
Step by step solution
01
- Identify the Domain
To determine the domain of the function \( g(x) = \ln(x-1) \), we need to identify the values of \( x \) for which the function is defined. Since the natural logarithm function \( \ln(y) \) is only defined for \( y > 0 \), we need \( x-1 > 0 \). Solving this inequality, we get \( x > 1 \). Thus, the domain is \( (1, \infty) \).
02
- Identify the Range
The range of the natural logarithm function \( \ln(y) \) is all real numbers \( (-\infty, \infty) \). Since there are no restrictions on the output of the natural logarithm, the range of \( g(x) = \ln(x-1) \) is also \( (-\infty, \infty) \).
03
- Graph the Function
To graph \( g(x) = \ln(x-1) \), start by shifting the graph of \( y = \ln(x) \) to the right by 1 unit. The vertical asymptote, originally at \( x = 0 \) for \( y = \ln(x) \), will shift to \( x = 1 \). The graph will be defined for all \( x > 1 \) and will increase slowly to the right while approaching negative infinity as \( x \) approaches 1 from the right.
04
- Verify the Function Behavior
Check points to verify: For \( x = 2 \), \( g(2) = \ln(2-1) = \ln(1) = 0 \). For \( x = 3 \), \( g(3) = \ln(3-1) = \ln(2) \), which is approximately 0.693. These points ensure the accuracy of the graph.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
natural logarithm
The natural logarithm, represented as \(\ln(x)\), is a logarithmic function with the base \(e e\), where \(e\) is an irrational and transcendental number approximately equal to 2.71828. The natural logarithm of a number is the power to which \(e\) must be raised to obtain that number. Importantly, \(\ln(x)\) is only defined for positive values of \(x\), meaning \(x > 0\).Properties of the Natural Logarithm:
- \(\ln(1) = 0\) because \(e^0 = 1\).
- \(\ln(e) = 1\) because \(e^1 = e\).
- The natural logarithm function is continuous and increases without bound, but at a decreasing rate.
graphing functions
Graphing functions helps us visualize their behavior and characteristics. For the function \(g(x) = \ln(x-1)\), we can follow these steps to create its graph:Step-by-Step Graphing Guide:
- Identify the base function: Start with the graph of \(y = \ln(x)\). This curve passes through the point \((1, 0)\) and approaches negative infinity as \(x\) approaches zero from the right.
- Shift the graph horizontally: Since our function is \(g(x) = \ln(x-1)\), we shift the entire graph of \(y = \ln(x)\) one unit to the right. This places the vertical asymptote at \(x = 1\).
- Plot key points: Verify specific points on the graph. For instance, when \(x = 2\), \(g(2) = \ln(1) = 0\). Likewise, when \(x = 3\), \(g(3) = \ln(2) \approx 0.693\).
vertical asymptote
A vertical asymptote is a line that a graph approaches but never touches or crosses. It represents values where the function grows infinitely large or small. In the context of \(g(x) = \ln(x-1)\), the vertical asymptote occurs at \(x = 1\).Understanding Vertical Asymptotes:
- Vertical asymptotes are found by determining the values for which the function is undefined or tends towards infinity.
- For natural logarithm functions, such as \(g(x) = \ln(x-1)\), the vertical asymptote is determined by setting the argument of the logarithm equal to zero. So, \(x-1 = 0\) implies \(x = 1\).