Chapter 2: Problem 64
A function \(f\) is given. (a) Sketch the graph of \(f .\) (b) Use the graph of \(f\) to sketch the graph of \(f^{-1}\). (c) Find \(f^{-1}\). $$f(x)=x^{3}-1$$
Short Answer
Expert verified
Inverse function is \( f^{-1}(x) = \sqrt[3]{x + 1} \).
Step by step solution
01
Understanding the Function
The given function is \( f(x) = x^3 - 1 \). This is a cubic function that has been translated one unit down. The basic cubic function \( x^3 \) is symmetric about the origin, and the translation modifies it.
02
Sketching the Graph of \( f \)
Plot the graph of \( f(x) = x^3 - 1 \). It starts at \( (-1, 0) \) on the y-axis, with the point \( x = 0 \) mapped to \( f(0) = -1 \). As \( x \) increases or decreases, the graph follows the typical cubic shape, flattening around the origin.
03
Understanding the Inverse Function
To find the inverse function, \( f^{-1} \), we need to swap the roles of \( x \) and \( y \). So, for \( f(x) = x^3 - 1 \), the inverse will reverse the operation of subtracting 1 and then taking the cube root.
04
Sketching the Graph of \( f^{-1} \)
To sketch \( f^{-1} \), reflect the graph of \( f \) across the line \( y = x \). The graph of \( f^{-1} \) will pass through the points \( (0, -1) \), \( (-1, 0) \), and it will have an inverse cubic shape.
05
Finding \( f^{-1} \) Algebraically
Starting with \( y = x^3 - 1 \), solve for \( x \) in terms of \( y \). First, add 1 to both sides to obtain \( y + 1 = x^3 \). Then, take the cube root of both sides to find \( x = \sqrt[3]{y + 1} \). Therefore, the inverse function is \( f^{-1}(x) = \sqrt[3]{x + 1} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Cubic Function
A cubic function is a polynomial of degree 3 and often takes the form \( f(x) = ax^3 + bx^2 + cx + d \), where \( a, b, c, \) and \( d \) are constants, and \( a eq 0 \). The simplest form of a cubic function is \( f(x) = x^3 \), which is symmetric about the origin.
Cubic functions display a few distinct characteristics:
Cubic functions display a few distinct characteristics:
- They can have one or three real roots.
- Their graphs exhibit points of inflection, where the curve changes concavity.
- The end behavior means as \( x \to \pm \infty \), \( f(x) \to \pm \infty \) respectively if \( a > 0 \), or \( f(x) \to \mp \infty \) if \( a < 0 \).
Graph Sketching
Graph sketching is a crucial strategy in understanding the overall behavior of functions. For a cubic function like \( f(x) = x^3 - 1 \), starting with key characteristics helps make the sketch more accurate.
Here's how to approach sketching:
Here's how to approach sketching:
- Identify Critical Points: Find where the function intersects the axes. For \( f(x) = x^3 - 1 \), the intersection is at points like \( (0, -1) \).
- Analyze Behavior Near the Origin: Notice how the function behaves around \( x = 0 \), since cubic functions tend to flatten near inflection points.
- Examine End Behavior: As \( x \) heads towards \( \pm \infty \), \( f(x) \) carries the graph upwards or downwards depending on the lead coefficient.
- Enhance with Specific Points: Calculating values for specific \( x \) values can provide additional plot points to ensure accuracy.
Function Transformation
Function transformations allow us to modify the basic graph of functions in predictable ways. The expression \( f(x) = x^3 - 1 \) reflects a transformation of the base function \( x^3 \) by shifting it one unit downwards.
Function transformations primarily include:
Function transformations primarily include:
- Vertical Shifts: Adding or subtracting a constant shifts the graph up or down. \( x^3 - 1 \) means shifting downward.
- Horizontal Shifts: Adding or subtracting inside the function argument would shift the graph left or right, but there is none here.
- Stretching/Compressing: Multiplying the function or variable by constants influences its steepness and overall spread.