Chapter 4: Problem 45
Sketch the graph of \(f\). $$f(x)=\log _{2}\left(x^{3}\right)$$
Short Answer
Expert verified
The graph of \( f(x) = \log_{2}(x^3) \) is a logarithmic curve starting from \(-\infty\) near \( x=0 \), passing through (1,0), and increasing to \(\infty\).
Step by step solution
01
Identify the Domain
To find the domain of the function \( f(x) = \log_{2}(x^3) \), we need \( x^3 > 0 \), because the logarithm is only defined for positive numbers. This means \( x > 0 \). Thus, the domain of \( f(x) \) is \( x > 0 \).
02
Analyze Behavior at Critical Points
Consider special points to understand behavior. At \( x = 1 \), we have \( f(1) = \log_{2}(1^3) = \log_{2}(1) = 0 \). As \( x \to 0^+ \), \( x^3 \to 0^+ \), thus \( f(x) = \log_{2}(x^3) \to -\infty \).
03
Determine End Behavior
Evaluate the function as \( x \to \infty \). Since \( x^3 \to \infty \) as \( x \to \infty \), \( f(x) = \log_{2}(x^3) = 3 \cdot \log_{2}(x) \to \infty \). This indicates the graph of \( f(x) \) keeps increasing with no upper bound.
04
Sketch the Graph
Based on the analysis, sketch the graph: Start near the origin, approaching the vertical asymptote at \( x = 0 \), passing through the point (1,0), and continue to increase without bound as \( x \to \infty \). The graph is smooth and continuously increasing, reflecting the behavior of a logarithmic function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Domain of a Function
In mathematics, the domain of a function refers to the set of all possible input values (usually represented by \(x\)) for which the function is defined. For the function \(f(x) = \log_{2}(x^3)\), understanding the domain is crucial because logarithmic functions are only defined for positive arguments. This means, for our specific function:
- We need \(x^3 > 0\).
- This simplifies to \(x > 0\) because any negative value of \(x\) cubed remains negative.
Asymptotic Behavior
The asymptotic behavior of a function describes how it behaves as it approaches certain limits or boundaries. For logarithmic functions like \(f(x) = \log_{2}(x^3)\), vertical asymptotes are common. Here:
- When \(x\) approaches 0 from the positive side (denoted as \(x \to 0^+\)), \(x^3\) tends toward zero, meaning the input of the log approaches zero.
- Since \(\log_{2}(x^3)\) tends to negative infinity as \(x^3\) approaches zero, there is a vertical asymptote at \(x = 0\).
Graphing Functions
When graphing a function, especially a logarithmic one like \(f(x) = \log_{2}(x^3)\), it involves plotting points that represent the function's values for various inputs of \(x\), then drawing a curve that smoothly connects these points.
- Begin by noting the point it passes through known values: for example, \(f(1) = \log_{2}(1^3) = 0\).
- From this point, we know the function starts at (1,0) on the graph.
- The function increases continuously as \(x\) increases, with the curve rising to the right without bound.
End Behavior
End behavior in functions describes how a graph behaves as \(x\) goes towards infinity or negative infinity. For the function \(f(x) = \log_{2}(x^3)\):
- As \(x \to \infty\), \(x^3\) also tends toward infinity.
- Therefore, \(f(x) = \log_{2}(x^3)\) continues to rise without bound.
- Explicitly, \(f(x) = 3 \log_{2}(x)\), indicating a continuously increasing curve.