Chapter 5: Problem 48
Sketch a graph of \(y=f(x)\) $$ f(x)=3\left(2^{-x}\right) $$
Short Answer
Expert verified
The graph is a decreasing exponential curve approaching the \( x \)-axis as \( x \) increases.
Step by step solution
01
Identify the Function Type
The given function is an exponential function: \( f(x) = 3(2^{-x}) \). This type of function decreases as \( x \) increases because it has a negative exponent.
02
Determine Key Points
Choose a few values of \( x \) to determine the corresponding \( y \) values: \( f(0) = 3(2^0) = 3 \), \( f(1) = 3(2^{-1}) = \frac{3}{2} \), \( f(-1) = 3(2^{1}) = 6 \), and \( f(2) = 3(2^{-2}) = \frac{3}{4} \).
03
Analyze Asymptotic Behavior
As \( x \) approaches infinity, \( 2^{-x} \) approaches 0, so \( f(x) \) approaches the horizontal asymptote \( y = 0 \).
04
Plot the Points
Plot the points \((0,3)\), \((1,1.5)\), \((2,0.75)\), and \((-1,6)\) on a Cartesian plane, showing the decreasing nature of the function.
05
Draw the Sketch
Connect the points with a smooth curve, starting high on the left, decreasing while moving to the right, getting closer to \( y=0 \), but never touching it.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graph Sketching
When sketching the graph of an exponential function like \( f(x) = 3(2^{-x}) \), it's important to remember that the base and the exponent play key roles in determining the graph's features. The general form of an exponential function is \( a \cdot b^x \), where \( a \) is the initial value or the vertical stretch factor, and \( b \) is the base that dictates growth or decay. In our function, \( a = 3 \) and \( b = 2^{-1} \).
Steps to sketch the graph include:
Steps to sketch the graph include:
- Select several values of \( x \) and calculate the corresponding \( y \) values for those points. For example, when \( x = 0 \), \( y = 3 \); when \( x = 1 \), \( y = 1.5 \); and so on.
- Plot these points on a Cartesian coordinate system to help visualize the graph.
- Connect these points smoothly to show the behavior of the function, noting how it decreases.
Asymptotic Behavior
The term "asymptotic behavior" refers to how a function behaves as it moves towards infinity or negative infinity. For an exponential decay function like \( f(x) = 3(2^{-x}) \), the significant asymptote is the horizontal line \( y = 0 \). This line represents a value that the function approaches but never actually reaches.
Understanding asymptotes is crucial because:
Understanding asymptotes is crucial because:
- They help determine the end behavior of the graph.
- They indicate leveling patterns as the function values get smaller with increasing or decreasing \( x \).
Function Transformation
Function transformation allows us to modify the basic form of functions and explore how these changes affect their graphs. For \( f(x) = 3(2^{-x}) \), this involves shifts, stretches, and reflections derived from changing parameters and exponents.
Key transformations are:
Key transformations are:
- Vertical Stretch: The factor \( 3 \) stretches the basic graph vertically, influencing the amplitude of the function.
- Reflection: The negative exponent \(-x\) reflects the base function \(2^x\) across the y-axis, turning it into a decay function.