Chapter 4: Problem 200
For the following exercises, state the domain and the vertical asymptote of the function. $$g(x)=\ln (3-x)$$
Short Answer
Expert verified
Domain: \(x < 3\); Vertical Asymptote: \(x = 3\).
Step by step solution
01
Understanding the Domain
The domain of a function describes all the possible values of x for which the function is defined. Since we are dealing with the natural logarithm, the expression inside the logarithm must be greater than zero, i.e., \(3-x > 0\).
02
Solving for Domain
To find the domain, solve the inequality \(3-x > 0\). Rearranging gives \(x < 3\). Thus, the domain of the function \(g(x) = \ln(3-x)\) is all x such that \(x < 3\). In interval notation, this is \((-fty, 3)\).
03
Identifying the Vertical Asymptote
A vertical asymptote typically occurs where the function is undefined due to the input approaching a critical value. Here, \(x = 3\) is where \(3-x = 0\) (thus, \(g(x)\) is undefined for \(x \geq 3\)). Therefore, the vertical asymptote is \(x = 3\).
04
Conclusion
The domain of \(g(x) = \ln(3-x)\) is \(x < 3\) and the vertical asymptote is \(x = 3\).
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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 is a fundamental mathematical function denoted by \( \ln(x) \). It is the inverse of the exponential function \( e^x \), which means that \( \ln(e^x) = x \). The natural logarithm has several important properties:
- Defined for Positive Values: The natural logarithm is only defined for positive values of \( x \). This implies that when dealing with expressions within a logarithm, ensure the expression is greater than zero.
- Relationship with Exponentials: Since it is the inverse of the exponential, \( \ln(e) = 1 \) and \( \ln(1) = 0 \).
- Simplifying Expressions: Inequalities involving the logarithm often guide us in determining valid inputs, helping to define function domains.
Vertical Asymptote
A vertical asymptote of a function is a vertical line \( x = a \) where the function approaches infinity or negative infinity as \( x \) approaches \( a \). This usually occurs when a function is undefined for a particular value of \( x \).To find a vertical asymptote:
- Identify where the function is undefined. Often this involves setting the denominator to zero or evaluating critical points like in the expression provided by a logarithm.
- In the problem involving \( g(x) = \ln(3-x) \), the vertical asymptote is at \( x = 3 \). This is because substituting \( x = 3 \) into the function gives \( \ln(0) \), which is undefined.
- Approaching the asymptote, the function’s value increases or decreases without bound, graphically showing the asymptotic behavior near \( x = 3 \).
Inequalities
Inequalities are statements that compare two expressions using symbols such as \( < \), \( > \), \( \leq \), or \( \geq \). Solving inequalities involves finding the range of values that satisfy the given condition.In the context of determining the domain of \( g(x) = \ln(3-x) \):
- We need to solve the inequality \( 3-x > 0 \) to ensure the logarithm is well-defined. Rearranging gives \( x < 3 \), constraining \( x \) to values less than 3.
- The solution to the inequality provides all the acceptable values for \( x \), forming the domain of the function.
- Representing the domain using interval notation, we find it to be \( (-\infty, 3) \), clearly excluding the point where the function becomes undefined (\( x = 3 \)).