Chapter 3: Problem 28
Graph the exponential function using transformations. State the \(y\) -intercept, two additional points, the domain, the range, and the horizontal asymptote. $$f(x)=7^{x}$$
Short Answer
Expert verified
The y-intercept is (0,1). Additional points are (1,7) and (-1,1/7). Domain: \((-\infty, \infty)\), Range: \((0, \infty)\), Horizontal asymptote: \(y = 0\).
Step by step solution
01
Understand the Base Graph
The base graph for this function is the exponential function \( f(x) = 7^x \), which has the general shape of an exponential growth curve. It passes through the point (0,1) because any number to the power of 0 equals 1.
02
Identify the Exponential Function Characteristics
Since \( f(x) = 7^x \) has no transformations like shifts or stretches, the graph retains its basic exponential shape passing through (0,1), (1,7), and (-1, \(\frac{1}{7}\)).
03
Determine the Y-intercept
The y-intercept occurs where \( x = 0 \). Since \( f(0) = 7^0 = 1 \), the y-intercept is at (0,1).
04
Find Additional Points
To find two more points, evaluate the function at \( x = 1 \) and \( x = -1 \):- For \( x = 1 \), \( f(1) = 7^1 = 7 \), so a point is (1,7).- For \( x = -1 \), \( f(-1) = 7^{-1} = \frac{1}{7} \), so a point is (-1, \frac{1}{7}).
05
Determine the Domain
The domain of \( f(x) = 7^x \) is all real numbers, written as \((-\infty, \infty)\).
06
Determine the Range
The range of the exponential function \( f(x) = 7^x \) is \((0, \infty)\) because the function never reaches 0 and continues to increase.
07
Identify the Horizontal Asymptote
The horizontal asymptote of the function \( f(x) = 7^x \) is \( y = 0 \) because as \( x \) approaches negative infinity, \( f(x) \) approaches 0, but never touches it.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Transformations
When graphing exponential functions like \( f(x) = 7^x \), understanding transformations can greatly simplify the process. As a fundamental exponential function, \( 7^x \) does not initially involve transformations such as shifts, stretches, or compressions. However, understanding these concepts is key to graphing more complex versions of exponential functions.
- **Vertical Shifts**: This occurs when a constant is added or subtracted from the function, shifting the graph up or down.
- **Horizontal Shifts**: When you modify the variable \( x \) by adding or subtracting within the exponent, the graph shifts left or right.
- **Reflections**: Multiplying by a negative results in flipping the graph across the x or y-axis.
Domain and Range
The domain and range define where the function exists on a graph. For \( f(x) = 7^x \), understanding these concepts helps in interpreting and narrowing down the focus of the graph.This function exhibits the classic characteristics of an exponential growth function:- **Domain**: The domain of \( 7^x \) includes all real numbers, \((-\infty, \infty)\). This means that \( x \) can take any real number value, reinforcing the notion that exponential functions are continuously defined.- **Range**: The range of \( 7^x \) is \((0, \infty)\). This indicates that no matter what value \( x \) takes, the output \( f(x) \) will always be a positive number, but never zero.
Horizontal Asymptote
In exponential functions such as \( f(x) = 7^x \), the horizontal asymptote is a critical component that describes the graph's end behavior.- **Horizontal Asymptote**: Here, the function approaches a y-value that it will get infinitely close to, but never actually reach. For \( 7^x \), that asymptote is at \( y = 0 \). As \( x \) moves towards negative infinity, \( f(x) \) approaches zero but does not touch or cross the x-axis.Horizontal asymptotes are a hallmark of exponential decay and growth, offering insights into the function's limit behavior.
Exponential Growth
Exponential growth defines how the function \( f(x) = 7^x \) behaves and increases as \( x \) increases. The nature of exponential functions allows them to rise rapidly after a certain point.- **Initial Value and Growth**: Starting from it’s y-intercept at (0,1), the function demonstrates that any increase in \( x \) results in a proportionately larger increase in \( f(x) \). This stems from the base value (in this case, 7) raised to the power of \( x \).- **Growth Curve**: The points (0,1), (1,7), and (-1, \( \frac{1}{7} \)) highlight this steep upward trajectory, showcasing how quickly the function can spike upwards.Exponential growth is a key feature for diverse applications, from population growth models to financial calculations, making understanding these functions essential.