Chapter 5: Problem 80
Graph the function and its inverse using the same set of axes. Use any method. $$f(x)=\log _{4} x, f^{-1}(x)=4^{x}$$
Short Answer
Expert verified
Graph \( f(x) = \log_{4} x \) and \( f^{-1}(x) = 4^x \) on the same axes, with the line \( y = x \).
Step by step solution
01
- Understand the Functions
We have two functions: the original function is \( f(x) = \log_{4} x \) and the inverse function is \( f^{-1}(x) = 4^x \). The original function takes the logarithm base 4 of \( x \) and the inverse function raises 4 to the power of \( x \).
02
- Determine Key Points for \( f(x) \)
To graph \( f(x) = \log_{4} x \), determine key points by choosing values of \( x \) for which \( f(x) \) is easily found: \( (1, 0), (4, 1), (16, 2) \) since \( \log_{4} 1 = 0 \), \( \log_{4} 4 = 1 \), and \( \log_{4} 16 = 2 \). Outline these points.
03
- Plot \( f(x) \)
On the coordinate system, plot the points: \( (1, 0), (4, 1), (16, 2) \). These support the logarithmic curve in the positive \( x \)-axis direction.
04
- Determine Key Points for \( f^{-1}(x) \)
For \( f^{-1}(x) = 4^x \), choose \( x \) values: \( (-1, \frac{1}{4}), (0, 1), (1, 4), (2, 16) \) since \( 4^{-1} = \frac{1}{4} \), \( 4^0 = 1 \), \( 4^1 = 4 \), and \( 4^2 = 16 \).
05
- Plot \( f^{-1}(x) \)
On the same coordinate system, plot the points: \( (-1, \frac{1}{4}), (0, 1), (1, 4), (2, 16) \). These create the exponential growth curve.
06
- Draw the Line y=x
Draw the line \( y = x \) on the graph. This line aids in visualizing symmetry between \( f(x) \) and \( f^{-1}(x) \). Each point on \( f(x) \) swaps along this line to become a matching point on \( f^{-1}(x) \), confirming they are reflections.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Logarithmic Functions
Logarithmic functions are essential in mathematics and real-world applications. For the function provided, \( f(x) = \log_{4} x \), 'log' represents logarithm, and '4' is the base. A logarithm answers the question: 'To what exponent must the base be raised, to produce a given number?'. In simple terms, \( \log_{4} 16 = 2 \) because raising 4 to the power of 2 gives 16. Understanding this relationship helps in graphing the function accurately. To get neat points on the graph, choose x-values that are easy for calculations:
- \(\log_{4} 1 = 0\) (since \(4^0 = 1\))
- \(\log_{4} 4 = 1\) (since \(4^1 = 4\))
- \(\log_{4} 16 = 2\) (since \(4^2=16\))
Exponential Functions
Exponential functions are another cornerstone of mathematics. They often describe rapid growth or decay. For the inverse function given, \( f^{-1}(x) = 4^x \), '4' is the base, and x is the exponent. This function grows quickly, unlike the slow rise of the logarithmic function. Think about how 4 raised to different powers gives us new y-values:
- \( 4^{-1} = \frac{1}{4} \)
- \( 4^{0} = 1 \)
- \( 4^{1} = 4 \)
- \( 4^{2} = 16 \)
Graphing Techniques
Graphing functions requires plotting points and drawing curves that connect them. It helps to start with points you calculated:
- For \( f(x) = \log_{4} x \): \((1, 0), (4, 1), (16, 2)\)
- For \( f^{-1}(x) = 4^x \): \((-1, \frac{1}{4}), (0, 1), (1, 4), (2, 16)\)
Symmetry in Functions
Symmetry is a powerful tool in understanding functions and their inverses. For a function \( f(x) \) and its inverse \( f^{-1}(x) \), the line \( y = x \) acts as a mirror. This line helps to visualize how the graph of \( f(x) = \log_{4} x \) and \( f^{-1}(x) = 4^x \) are reflections of each other. Each point \((a, b)\) on \( f(x) \) corresponds to the point \((b, a)\) on \( f^{-1}(x) \). For example:
- \((1, 0)\) on \( f(x) = \log_{4} x \) reflects to \((0, 1)\) on \( f^{-1}(x) = 4^x \)
- \((4, 1)\) on \( f(x) \) reflects to \((1, 4)\) on \( f^{-1}(x) \)
- \((16, 2)\) corresponds to \((2, 16)\)