Chapter 2: Problem 71
Let the domain of \(f(x)\) be \([-1,2]\) and the range be \([0,3] .\) Find the domain and range of the following. $$3 f\left(\frac{1}{4} x\right)$$
Short Answer
Expert verified
Domain: [-4, 8], Range: [0, 9]
Step by step solution
01
Identify the Transformation Operations
The expression given is \( 3f\left(\frac{1}{4}x\right) \). There are two transformations applied: \( f\left(\frac{1}{4}x\right) \) is a horizontal stretch by a factor of 4, and \( 3f(x) \) is a vertical stretch by a factor of 3.
02
Adjust the Domain for Horizontal Stretch
The original domain is \([-1, 2]\). The function \( f\left(\frac{1}{4}x\right) \) stretches the domain by a factor of 4. To find the new domain, multiply each endpoint of the original domain by 4. Thus, \(-1 \times 4 = -4\) and \(2 \times 4 = 8\), giving us the new domain \([-4, 8]\).
03
Adjust the Range for Vertical Stretch
The original range is \([0, 3]\). The function \( 3f(x) \) stretches the range by a factor of 3. To find the new range, multiply each endpoint of the original range by 3. Thus, \(0 \times 3 = 0\) and \(3 \times 3 = 9\), giving us the new range \([0, 9]\).
04
Combine Transformed Domain and Range
After applying the transformations, the new domain becomes \([-4, 8]\) and the new range becomes \([0, 9]\). This reflects the composition of both transformations on the function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Horizontal Stretch
A horizontal stretch affects how a function behaves along the x-axis, widening the graph out horizontally. It alters the way points are distributed over the x-axis by stretching or compressing them. For instance, when you have a function such as \( f\left(\frac{1}{4}x\right) \), it means you will stretch the x-values four times further apart.
Here’s what you need to remember about horizontal stretches:
Here’s what you need to remember about horizontal stretches:
- They change the domain of the function.
- The factor by which you multiply the x-coordinates is the reciprocal of what appears inside the function with x. So, \(\frac{1}{4}\) becomes 4 as the stretching factor.
- The original domain end-points of \([-1, 2]\) will be transformed by multiplying them by 4, widening them to \([-4, 8]\).
Exploring Vertical Stretch
Vertical stretch involves the y-axis, influencing the output values of a function. It effectively pulls the graph upwards or downwards, amplifying or diminishing the effect. In the vertical stretch case, like \( 3f(x) \), each y-coordinate is three times as far from the x-axis than it was originally.
Key points to note about vertical stretches:
Key points to note about vertical stretches:
- They modify the range of the function.
- Every y-value is multiplied by the stretch factor. In our example, this factor is 3.
- The original range \([0, 3]\) scales up to \([0, 9]\) when multiplied by 3.
Domain and Range Transformations
When functions undergo transformations, understanding how domain and range change is crucial. During a horizontal or vertical stretch, these transformations modify where and how the function plots on a graph.
Let’s break it down:
Let’s break it down:
- **Domain Transformations**: These are related to horizontal changes. With a horizontal stretch by factor 4, each element of the domain \([-1, 2]\) is magnified, resulting in the new domain \([-4, 8]\).
- **Range Transformations**: Pertaining to vertical changes, such as multiplying a function by 3, which swells the range from \([0, 3]\) to \([0, 9]\).