Chapter 4: Problem 17
Sketch the graph of \(f\) $$f(x)=-\left(\frac{1}{2}\right)^{x}+4$$
Short Answer
Expert verified
Reflect the base graph across the x-axis and shift up by 4 units.
Step by step solution
01
Identify the base graph
Start by identifying the base graph, which is a simple exponential function. The base graph is given by \(g(x) = \left(\frac{1}{2}\right)^x\). This is a decreasing exponential function.
02
Apply the reflection
The function \(f(x) = -\left(\frac{1}{2}\right)^x+4\) includes a negative sign in front of the base function. This means reflect the graph of \(g(x)\) over the x-axis. If the original graph of \(g(x)\) was above the x-axis, the reflection will put it below the x-axis, maintaining its decreasing nature.
03
Vertical shift
The \(+4\) in \(f(x) = -\left(\frac{1}{2}\right)^x + 4\) indicates a vertical shift. Shift the entire reflected graph up by 4 units. This changes the horizontal asymptote from \(y = 0\) (the x-axis) to \(y = 4\).
04
Sketch the graph
Taking into account the reflection and vertical shift, draw the graph starting as a horizontal line near \(y = 4\) and decreasing towards it, but remaining under the x-axis for large negative \(x\). For \(x = 0\), calculate \(f(0) = -1 + 4 = 3\), and plot this point as it is above the x-axis.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Exponential Functions
Exponential functions are mathematical expressions where a constant base is raised to a variable exponent. A general form of an exponential function is given by \(a^\{x\}\), where \'a\' is a positive real number, and \'x\' is the variable. Depending on the base, an exponential function can either increase or decrease:
- If \(a > 1\), the function exponentially increases.
- If \(0 < a < 1\), the function exponentially decreases.
Exploring Graph Transformations
Graph transformations are methods used to alter the appearance of a graph without changing its core properties. These transformations include changes in position, orientation, and size.
Basic transformations can be summarized as follows:
Basic transformations can be summarized as follows:
- Shifts: Move the graph horizontally or vertically.
- Stretching and Compressing: Change the width or height of the graph.
- Reflections: Flip the graph across an axis.
Reflection Across the X-Axis
Reflection involves flipping a graph over a specific axis, creating a mirror image. When a function is multiplied by \(-1\), it flips across the x-axis.
In the example from the exercise, the exponential function \(g(x) = \left(\frac{1}{2}\right)^x\) becomes \(-\left(\frac{1}{2}\right)^x\). This reflection inverts the graph, causing points that were originally above the x-axis to now appear below it. Despite changing its position, the reflected graph retains its decreasing nature.
Reflections are a critical tool in graph transformations, providing a straightforward way to change the direction of a function's growth or decay while preserving its shape.
In the example from the exercise, the exponential function \(g(x) = \left(\frac{1}{2}\right)^x\) becomes \(-\left(\frac{1}{2}\right)^x\). This reflection inverts the graph, causing points that were originally above the x-axis to now appear below it. Despite changing its position, the reflected graph retains its decreasing nature.
Reflections are a critical tool in graph transformations, providing a straightforward way to change the direction of a function's growth or decay while preserving its shape.
Understanding Vertical Shifts
Vertical shifts involve moving the entire graph up or down along the y-axis. This transformation is achieved by adding or subtracting a constant to the function.
For the function \(f(x) = -\left(\frac{1}{2}\right)^x + 4\), the \(+4\) causes a vertical shift upwards by 4 units. This shift alters the graph's asymptote from \(y = 0\) to \(y = 4\).
Vertical shifts do not change the shape of the graph but redefine its position along the y-axis. These shifts are essential for adjusting the baseline level in various applications, such as accounting for an initial quantity in scientific models.
For the function \(f(x) = -\left(\frac{1}{2}\right)^x + 4\), the \(+4\) causes a vertical shift upwards by 4 units. This shift alters the graph's asymptote from \(y = 0\) to \(y = 4\).
Vertical shifts do not change the shape of the graph but redefine its position along the y-axis. These shifts are essential for adjusting the baseline level in various applications, such as accounting for an initial quantity in scientific models.