Chapter 10: Problem 92
Graph each logarithmic function. $$f(x)=\log _{1 / 5} x$$
Short Answer
Expert verified
Plot points (5, -1), (1, 0), and (\( \frac{1}{5} \), 1) and draw a decreasing curve, approaching \(x = 0\) asymptotically.
Step by step solution
01
Understand the Function
The given function is \(f(x) = \log_{1/5} x\). This notation means that we are dealing with a logarithm with base \(\frac{1}{5}\). Understanding that this base is less than 1 is crucial because it affects the shape and direction of the graph.
02
Determine Key Points
To graph \(f(x) = \log_{1/5} x\), select key points by converting the logarithmic form \(y = \log_{1/5} x\) into the exponential form: \(x = \left(\frac{1}{5}\right)^y\). Pick values for \(y\) and solve for \(x\). For example, when \(y = -1\), \(x = 5\); when \(y = 0\), \(x = 1\); when \(y = 1\), \(x = \frac{1}{5}\).
03
Create a Table of Values
Construct a table with the chosen key points:\[\begin{array}{c|c}y & x \ \hline-1 & 5 \ 0 & 1 \ 1 & \frac{1}{5} \ \end{array}\]
04
Plot the Points
On a coordinate plane, plot the points from your table: (5, -1), (1, 0), and (\( \frac{1}{5} \), 1).
05
Draw the Curve
Draw a smooth curve through the points, remembering that the logarithmic function concerning the base \(\frac{1}{5}\) will decrease as \(x\) increases. The graph will approach the vertical asymptote at \(x = 0\) but will never touch or cross it.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
logarithmic function
A logarithmic function is a mathematical function defined as the inverse of an exponential function. In simpler terms, if you have an exponential function such as \( b^y = x \), the logarithmic form would be \( y = \log_b (x) \). This tells us that \( y \) is the exponent to which the base \( b \) must be raised to get \( x \).
For example, in \( f(x) = \log_{1/5} x \):
For example, in \( f(x) = \log_{1/5} x \):
- The base is \( \frac{1}{5} \)
- \( f(x) \) is the exponent.
base of a logarithm
The base of a logarithm is the number that is repeatedly multiplied by itself to produce a given value. In the function \( f(x) = \log_{1/5} x \), the base is \( \frac{1}{5} \). This means:
- To find the logarithm of a number, we determine the power (or exponent) we must raise \( \frac{1}{5} \) to, in order to get that number.
exponential form
Converting a logarithmic equation to an exponential form simplifies plotting key points on the graph.
For the function \( y = \log_{1/5} x \), we convert it to its exponential form: \( x = \left( \frac{1}{5} \right)^y \).
By converting back and forth between logarithmic and exponential forms, we can gather enough data points to plot an accurate graph.
For the function \( y = \log_{1/5} x \), we convert it to its exponential form: \( x = \left( \frac{1}{5} \right)^y \).
- This helps us identify key points (\( x, y \)) for graphing.
By converting back and forth between logarithmic and exponential forms, we can gather enough data points to plot an accurate graph.
vertical asymptote
A vertical asymptote is a line that a graph approaches but never touches or crosses. For logarithmic functions like \( f(x) = \log_{1/5} x \), the vertical asymptote is found where the function does not exist.
In this case:
In this case:
- The function does not exist for \( x \leq 0 \).