Chapter 12: Problem 42
Graph by hand. $$ f(x)=\log _{4} x $$
Short Answer
Expert verified
Plot points (1,0), (4,1), (16,2) and draw a curve that approaches but never touches the y-axis; label the graph.
Step by step solution
01
Understand the Function
The function given is a logarithmic function: \( f(x) = \log_{4}x \). This means that for any value of \( x \), the function returns the exponent to which 4 must be raised to get \( x \).
02
Identify Key Points
To graph \( f(x) = \log_{4}x \), identify some key points: 1. \( f(1) = \log_{4}1 = 0 \) because \( 4^0 = 1 \) 2. \( f(4) = \log_{4}4 = 1 \) because \( 4^1 = 4 \) 3. \( f(16) = \log_{4}16 = 2 \) because \( 4^2 = 16 \) These points help sketch the overall shape of the graph.
03
Set Up the Coordinate Plane
Draw a coordinate plane with the x-axis representing the values of \( x \) and the y-axis representing the values of \( f(x) \). Label the axes appropriately and mark a reasonable range for the x and y values based on the key points identified.
04
Plot Key Points
Plot the key points identified in Step 2 onto the coordinate plane: - (1, 0) - (4, 1) - (16, 2)
05
Draw the Curve
Draw a smooth curve that passes through the plotted points. Make sure the curve approaches the y-axis but never touches it, showing that \( \log_{4}(x) \) becomes very large and negative as \( x \) approaches zero.
06
Add Asymptote
Since \( \log_{4}x \) is undefined for \( x \leq 0 \), show that there is a vertical asymptote along the y-axis (x = 0). The graph will approach this line but never touch or cross it.
07
Label the Graph
Finally, label the graph of the function as \( f(x) = \log_{4}x \). Ensure the points and asymptote are clearly marked to complete the graph.
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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 type of function where the exponent is the variable. For example, in the function \( f(x) = \log_{4}x \), \( x \) is the argument of the logarithm with base 4. Logarithmic functions commonly represent exponential growth and decay in real-world scenarios.
Understanding the basic properties of the logarithm can help you comprehend these functions:
Understanding the basic properties of the logarithm can help you comprehend these functions:
- Logarithms undo exponentiation, meaning they find the exponent that a base must be raised to produce a certain number.
- The logarithmic function \( f(x) = \log_{b}x \) is only defined for positive \( x \) values, where \( b \) is the base and must be greater than 0 and not equal to 1.
- For any base \( b \), \( \log_b(1) = 0 \) because \( b^0 = 1 \).
Coordinate Plane
To graph a logarithmic function like \( f(x) = \log_{4}x \), you will use a coordinate plane, which has two perpendicular axes:
- The x-axis (horizontal) where you plot the values of \( x \).
- The y-axis (vertical) where you plot the corresponding function values \( f(x) \).
- Start by drawing the x-axis and y-axis and marking them with regular intervals.
- Label each axis to clarify which variable it represents.
- Choose a reasonable range for both axes based on the function and its key points. For example, if one of your key points is \( (1, 0) \), make sure your x-axis includes 1 and your y-axis includes 0.
- Mark important points and intervals that will help to accurately plot the graph of the function.
Vertical Asymptote
A vertical asymptote is a line that a graph approaches but never actually touches or crosses.
For logarithmic functions, vertical asymptotes occur where the function is undefined. In the case of \( f(x) = \log_{4}x \), the function is undefined for \( x \leq 0 \).
This means we have a vertical asymptote at \( x = 0 \). Graphically, you will:
For logarithmic functions, vertical asymptotes occur where the function is undefined. In the case of \( f(x) = \log_{4}x \), the function is undefined for \( x \leq 0 \).
This means we have a vertical asymptote at \( x = 0 \). Graphically, you will:
- Draw a dashed or dotted vertical line at \( x = 0 \).
- Make sure the curve you draw does not touch or cross this line.
Key Points
Key points are specific coordinates that help in sketching the graph of a function. For \( f(x) = \log_{4}x \), you can identify key points by plugging in values for \( x \) to find corresponding \( y \) values:
- \( (1, 0) \)
- \( (4, 1) \)
- \( (16, 2) \)
- For \( x=1 \), \( 4^0 = 1 \), giving the point \( (1, 0) \).
- For \( x=4 \), \( 4^1 = 4 \), giving the point \( (4, 1) \).
- For \( x=16 \), \( 4^2 = 16 \), giving the point \( (16, 2) \).