Chapter 6: Problem 8
Graph the function and its reflection about the y-axis on the same axes, and give the y-intercept. $$f(x)=3\left(\frac{1}{2}\right)^{x}$$
Short Answer
Expert verified
The y-intercept of both the function and its reflection is (0, 3).
Step by step solution
01
Identify the Function
The given function is \( f(x) = 3 \left( \frac{1}{2} \right)^x \). This is an exponential function where the base is \( \frac{1}{2} \). The multiplier of 3 is the coefficient that stretches or compresses the function vertically.
02
Plot the Original Function
To graph \( f(x) = 3 \left( \frac{1}{2} \right)^x \), choose several values of \( x \) and calculate \( f(x) \). For example, when \( x = 0 \), \( f(0) = 3 \times 1 = 3 \). When \( x = 1 \), \( f(1) = 3 \times \frac{1}{2} = 1.5 \). Plot these points, such as (0, 3), (1, 1.5), and continue for other values to create the curve.
03
Reflect the Function Across the Y-Axis
A reflection of a function \( f(x) \) about the y-axis is given by \( f(-x) \). So, find \( f(-x) = 3 \left( \frac{1}{2} \right)^{-x} = 3 \times 2^x \) for various values of \( x \). For instance, \( f(0) = 3 \), \( f(1) = 6 \), and so forth. Plot these points to create the reflection curve.
04
Determine the Y-intercept
The y-intercept occurs at \( x = 0 \). For both \( f(x) = 3 \left( \frac{1}{2} \right)^x \) and its reflection \( f(-x) = 3 \times 2^x \), the function values are the same: 3. Hence, the y-intercept for both functions is the point (0, 3).
05
Draw the Graph
Combine the plots created in Steps 2 and 3 on the same axes. The graph of \( f(x) = 3 \left( \frac{1}{2} \right)^x \) shows a decreasing exponential function, while the reflection \( f(-x) = 3 \times 2^x \) shows an increasing exponential function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Function Reflection
Reflecting a function on the y-axis essentially means flipping it horizontally. This transforms each point of the function to its mirror image concerning the y-axis. Let's explore this with the exponential function provided: - The original function is \( f(x) = 3 \left( \frac{1}{2} \right)^x \).- To reflect it across the y-axis, we replace \( x \) by \(-x\) in the function, giving us \( f(-x) = 3 \times 2^x \).Here's how reflection affects key characteristics:- **The curve's direction**: A reflection changes a decreasing function into an increasing one, and vice versa.- **The shape of the graph**: Remains the same distance from the y-axis on either side.Reflection is particularly useful for visualizing symmetrical behavior or for comparing function behavior under transformations.
Graphing Techniques
Graphing functions can seem daunting, but by following a systematic approach, it becomes a straightforward task. Here's a simple breakdown:1. **Selecting Points to Plot**: - Choose x-values that are easy to work with, such as 0, 1, -1, 2, etc. - For each x-value, calculate the corresponding y-value using the function. - For example, in our original function, \( f(x) = 3 \left( \frac{1}{2} \right)^x \), plug in values such as \( x = 0, 1, -1\) to get the y-values.2. **Plotting the Points**: - Mark these points on a coordinate plane (a grid where you plot graphs). - For a function like \( f(x) = 3 \left( \frac{1}{2} \right)^x \), you would plot points like (0, 3), (1, 1.5), etc.3. **Sketching the Curve**: - Once you've marked enough points, draw a smooth curve through them. - This will show the trend of the function, either increasing, decreasing, or following another pattern.Utilizing these techniques, even complex functions can be broken down into manageable parts, providing a clear visual understanding of function behavior.
Y-Intercept Calculation
Finding the y-intercept of a function involves determining where the function crosses the y-axis. By definition, the y-axis is where \( x = 0 \).- **For an exponential function** like \( f(x) = 3 \left( \frac{1}{2} \right)^x \), substitute \( x = 0 \) into the function: - Calculating this gives \( f(0) = 3 \times 1 = 3 \).- **For the reflected function** \( f(-x) = 3 \times 2^x \), do the same substitution: - Calculating \( f(-0) = 3 \times 1 = 3 \) confirms the y-intercept is also 3.This simple substitution provides quick insight, making the y-intercept one of the easiest points to determine. When graphing, the y-intercept is critical for accurately placing the function on the coordinate plane.