Chapter 1: Problem 77
Start with the graph of \(y=\ln x .\) Find an equation of the graph that results from a. shifting down 3 units. b. shifting right 1 unit. c. shifting left \(1,\) up 3 units. d. shifting down \(4,\) right 2 units. e. reflecting about the \(y\) -axis. f. reflecting about the line \(y=x\)
Short Answer
Expert verified
a. \(y = \ln x - 3\), b. \(y = \ln(x - 1)\), c. \(y = \ln(x + 1) + 3\), d. \(y = \ln(x - 2) - 4\), e. \(y = \ln(-x)\), f. \(y = e^x\).
Step by step solution
01
Shifting Down 3 Units
To shift the graph of a function down, we subtract a number from the function. The original function is \(y = \ln x\). By shifting it down 3 units, we have \(y = \ln x - 3\).
02
Shifting Right 1 Unit
To shift the graph of a function to the right, we replace \(x\) with \(x-c\) where \(c\) is the number of units moved. Shifting the graph of \(y= \ln x\) right by 1 unit results in \(y = \ln(x - 1)\).
03
Shifting Left 1, Up 3 Units
To shift the graph left 1 unit, replace \(x\) with \(x + 1\), and to shift up by 3 units, add 3 to the entire function. Therefore, \(y = \ln(x + 1) + 3\).
04
Shifting Down 4, Right 2 Units
First, shift the graph right 2 units by replacing \(x\) with \(x - 2\). Then, shift the graph down by subtracting 4. This results in the function \(y = \ln(x - 2) - 4\).
05
Reflecting About the y-axis
Reflecting a graph about the y-axis involves replacing \(x\) with \(-x\) in the function. For the original function \(y = \ln x\), the reflection is \(y = \ln(-x)\). Note that this results in a transformation that changes the domain of the function.
06
Reflecting About the Line y=x
Reflecting a graph about the line \(y=x\) involves swapping \(x\) and \(y\). The original equation \(y = \ln x\) becomes \(x = \ln y\). Solving for \(y\), we use exponentiation to get \(y = e^x\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graph Shifts
Graph shifts are a simple yet crucial concept in understanding function transformations. Whenever you move a graph from its original position on a coordinate plane, you are performing a graph shift. There are two primary types of shifts: vertical and horizontal.
Vertical shifts involve moving the graph up or down:
Vertical shifts involve moving the graph up or down:
- To shift a graph upward, you add a constant to the function. For instance, for the function \( y = \ln x \), shifting up by 3 units becomes \( y = \ln x + 3 \).
- Conversely, to move downward, you subtract a constant. Thus, \( y = \ln x - 3 \) shifts the graph down by 3 units.
- To shift right, subtract a constant from \( x \). For example, \( y = \ln(x - 1) \) shifts the graph right by 1 unit.
- To shift left, add a constant to \( x \). Therefore, \( y = \ln(x + 1) \) indicates a shift left by 1 unit.
Logarithmic Functions
Logarithmic functions are a specific type of function important in both mathematics and real-world applications like measuring sound intensity or earthquake magnitude. The base-\( e \) logarithmic function, also known as the natural logarithm, has a specific form:
Given as \( y = \ln x \), this function has notable characteristics.
Given as \( y = \ln x \), this function has notable characteristics.
- It is only defined for positive \( x \)-values because you cannot take the logarithm of zero or a negative number in real numbers.
- The graph of \( y = \ln x \) is steadily increasing but at a decreasing rate.
Reflection of Graphs
Reflections are a transformation that "flips" a graph over a specific line, producing a mirror image. In terms of functions, you can reflect over the y-axis or the line \( y = x \).
Reflecting over the y-axis involves changing \( x \) to \( -x \) in the function:
Reflecting over the y-axis involves changing \( x \) to \( -x \) in the function:
- For \( y = \ln x \), reflecting over the y-axis produces \( y = \ln(-x) \). This transformation affects the domain, as the logarithmic function is conventionally defined for positive values of \( x \).
- So \( y = \ln x \) becomes \( x = \ln y \), and when solved for \( y \), you get \( y = e^x \), introducing exponential functions into the reflection picture.
Translation of Functions
Translation of functions refers to moving a graph from one location to another on the plane without changing its shape, size, or orientation, functioning as a basis for understanding other complex transformations.
A straightforward translation combines both horizontal and vertical shifts. For instance:
A straightforward translation combines both horizontal and vertical shifts. For instance:
- Shifting the graph to the right by 2 units and down by 4 units results in \( y = \ln(x - 2) - 4 \).
- If translated left by 1 unit and up by 3 units, the function becomes \( y = \ln(x + 1) + 3 \).