Chapter 4: Problem 14
Graph the function, not by plotting points, but by starting from the graph of \(y=e^{x}\) in Figure \(1 .\) State the domain, range, and asymptote. $$g(x)=-e^{x-1}-2$$
Short Answer
Expert verified
Domain: all real numbers, Range: \(y < -2\), Asymptote: \(y = -2\).
Step by step solution
01
Identify the Base Graph
The base graph is given as \( y = e^x \). This is the standard exponential function with a horizontal asymptote at \( y = 0 \), a domain of all real numbers (\( x \in \mathbb{R} \)), and a range of positive real numbers (\( y > 0 \)).
02
Apply Horizontal Transformation
The given function is \( g(x) = -e^{x-1} - 2 \). Notice the \( x-1 \) part inside the exponent. This indicates a horizontal shift to the right by 1 unit. This doesn't affect the domain or the asymptote, but it shifts the graph.
03
Apply Reflection and Vertical Shift
The negative sign before \( e^{x-1} \) indicates a reflection about the x-axis. The \(-2\) indicates a vertical shift downward by 2 units. The horizontal asymptote, originally at \( y = 0 \), moves down to \( y = -2 \).
04
Determine Domain and Range
The domain remains all real numbers (\( x \in \mathbb{R} \)) because the transformations do not restrict the \( x \)-values. However, the range changes due to the reflection and the shift: all values less than \(-2\). Thus, the range is \( y < -2 \).
05
State the Asymptote
The horizontal asymptote, originally at \( y = 0 \), has been shifted down to \( y = -2 \) due to the vertical shift in the function equation.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponential Functions
Exponential functions form a vital part of mathematics due to their unique properties and applications. An exponential function is of the form \( y = a^{x} \), where \( a \) is a constant and \( x \) is the exponent. In this formula, \( a \) is known as the base, and it must be a positive number other than 1. One of the most common exponential functions is \( y = e^x \), where \( e \) is a mathematical constant approximately equal to 2.71828. This particular function is significant in various branches of science and engineering due to its natural growth properties.
- The domain of exponential functions like \( y = e^x \) is all real numbers, meaning \( x \) can be any real value.
- The range of \( y = e^x \) is always positive real numbers since the function output never becomes zero or negative.
- Exponential functions have unique characteristics, such as rapidly increasing or decreasing values, which can model real-world processes like population growth or radioactive decay.
Function Transformations
Function transformations involve shifting, stretching, reflecting, or compressing a function's graph without changing its basic shape. These transformations make it easier to understand relationships between different functions and their graphs. To transform the exponential function \( y = e^x \):
- A horizontal shift occurs when you have \( e^{x-c} \). The graph shifts \( c \) units to the right if \( c \) is positive, and \( |c| \) units to the left if \( c \) is negative.
- A vertical shift is introduced by adding or subtracting from the whole expression, like \( y = e^x + c \), moving the graph \( c \) units up or \( |c| \) units down.
- Reflection over the x-axis happens with a negative sign, as in \( y = -e^x \). This flips the graph upside down.
- A horizontal shift right by 1 unit.
- A reflection over the x-axis.
- A vertical shift down by 2 units.
Asymptotes
Asymptotes refer to lines that a graph approaches but never actually touches. They are especially important in graphing exponential functions. Knowing the asymptotes of a function helps to understand its behavior at the extremes. In a basic exponential function like \( y = e^x \), there is a horizontal asymptote at \( y = 0 \). This means, regardless of how large or small \( x \) becomes, \( y \) will never actually reach zero.
In transformations, asymptotes can shift. For \( g(x) = -e^{x-1} - 2 \), like the example above:
In transformations, asymptotes can shift. For \( g(x) = -e^{x-1} - 2 \), like the example above:
- The graph is horizontally shifted, but this does not affect the asymptote.
- The vertical shift of \(-2\) moves the asymptote from \( y = 0 \) to \( y = -2 \).
- The reflection does not change the location of the horizontal asymptote.