Chapter 4: Problem 37
(a) Sketch the graphs of \(f(x)=2^{x}\) and \(g(x)=3\left(2^{x}\right)\) (b) How are the graphs related?
Short Answer
Expert verified
The graphs of \(f(x)\) and \(g(x)\) are vertically scaled versions of each other, with \(g(x)\) stretched by a factor of 3.
Step by step solution
01
Understanding the Graphs
Before sketching the graphs, we need to understand the functions. The function \(f(x) = 2^x\) represents an exponential growth where the base is 2. The function \(g(x) = 3(2^x)\) is similar to \(f(x)\), but it is multiplied by 3, which affects the vertical stretching.
02
Sketching Graph 1: \(f(x) = 2^x\)
Plot the function \(f(x) = 2^x\). This graph is a typical exponential curve that starts below the x-axis for negative x-values, passes through the point (0, 1), and rises rapidly for positive x-values. It is always increasing and never touches the x-axis, showing exponential growth.
03
Sketching Graph 2: \(g(x) = 3(2^x)\)
Now plot the function \(g(x) = 3(2^x)\). This graph has the same shape as \(f(x) = 2^x\) because it is also an exponential curve. However, it passes through the point (0, 3) because every y-value of \(f(x)\) is multiplied by 3, indicating that \(g(x)\) is a vertically stretched version of \(f(x)\) by a factor of 3.
04
Comparing the Graphs
Notice that both graphs have the same base, so they have the same horizontal growth pattern. The graph of \(g(x) = 3(2^x)\) is a vertical stretch of the graph of \(f(x) = 2^x\) by a factor of 3. This means every point on \(f(x)\) is three times higher on \(g(x)\). The two graphs are similar in shape and orientation, but not in size.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graph Transformations
When we discuss graph transformations, we are focusing on how a graph's appearance can change by altering, shifting, or stretching it. For exponential functions like \(f(x) = 2^x\) and \(g(x) = 3(2^x)\), transformations are often visible in the vertical direction. A key transformation at play here is vertical stretching, but it's just one part of graph transformations. Here are a few types of transformations to be aware of:
- Translation: Moving the graph up, down, left, or right.
- Reflection: Flipping the graph over an axis.
- Vertical Stretch/Compression: Changing the height of the graph without altering the basic shape.
Exponential Growth
Exponential growth describes a situation where a quantity increases by a consistent percentage over equal intervals. For a function like \(f(x) = 2^x\), this is visually manifested as a curve that gets steeper as \(x\) gets larger. The base of the exponent, 2, means each step increases by a factor of 2. Here's why it's crucial:
- Dynamic Increase: There's no cap; values keep doubling, rising sharply on the graph.
- Real-World Examples: Population growth and compound interest are often modeled as exponential functions.
Vertical Stretching
Vertical stretching is a type of graph transformation that enlarges a graph in the vertical direction by multiplying all y-values by a constant factor. For instance, given \(f(x) = 2^x\) and its stretched form \(g(x) = 3(2^x)\), the number 3 causes each point on \(f(x)\) to be scaled up by three times its original height. Here's how to identify and analyze vertical stretching:
- Effect on Graph: While the shape and direction of the graph remain the same, the function reaches greater heights.
- Specific Changes: If \(f(0) = 1\) for \(f(x) = 2^x\), then \(g(0) = 3 \, \times \, 1 = 3\) for \(g(x) = 3(2^x)\).