Chapter 5: Problem 30
Give a complete graph of the function, and identify the location of all critical points and inflection poir s. Check your work with a graphing utility. $$4 x^{1 / 3}-x^{4 / 3}$$
Short Answer
Expert verified
Critical points at \( x = 0 \) and \( x = 1 \); inflection point at \( x = 2 \).
Step by step solution
01
Find the first derivative
To find critical points, we need the first derivative of the function. The function is given by \[ f(x) = 4x^{1/3} - x^{4/3}. \]The first derivative, using power rules, is\[ f'(x) = \frac{4}{3}x^{-2/3} - \frac{4}{3}x^{1/3}. \]
02
Solve for critical points
Critical points occur where the first derivative is zero or undefined. Set the first derivative to zero:\[ \frac{4}{3}x^{-2/3} - \frac{4}{3}x^{1/3} = 0. \]Factor out the common term:\[ \frac{4}{3}x^{-2/3}(1 - x) = 0. \]This gives two potential critical points: \( x = 0 \) and \( x = 1 \).
03
Find the second derivative
To find inflection points, we need the second derivative. The first derivative is:\[ f'(x) = \frac{4}{3}x^{-2/3} - \frac{4}{3}x^{1/3}. \] Differentiating again, we find\[ f''(x) = -\frac{8}{9}x^{-5/3} + \frac{4}{9}x^{-2/3}. \]
04
Solve for inflection points
Set the second derivative to zero to find potential inflection points:\[ -\frac{8}{9}x^{-5/3} + \frac{4}{9}x^{-2/3} = 0. \]Factor out the common term:\[ -\frac{4}{9}x^{-5/3}(2 - x) = 0. \]This implies that the second derivative changes sign at \( x = 2 \). Thus, the inflection point is \( x = 2 \).
05
Verify with a graphing utility
Using a graphing utility, plot the function \( f(x) = 4x^{1/3} - x^{4/3} \). Check if the graph shows critical points at \( x = 0 \) and \( x = 1 \), and an inflection point at \( x = 2 \). The graph should display these points accurately as confirmed by the graphing utility.
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Critical Points
Critical points of a function are vital in determining where the function's graph has peaks and valleys. To find these, we focus on where the first derivative equals zero or is undefined. Here's a basic process to identify critical points:
- Find the first derivative of the function.
- Set this derivative equal to zero and solve for the variable.
- Examine where the derivative is undefined, as these can also be critical points.
Inflection Points
Inflection points are where a curve changes concavity, from concave up to concave down, or the other way around. To determine where these points are, we use the second derivative.
- Find the second derivative of the function.
- Set this second derivative equal to zero and solve.
- Check where the second derivative changes sign, confirming a change in concavity.
Graphing Utilities
Graphing utilities are powerful tools for checking the accuracy of analytical solutions. They allow us to visualize a function and inspect critical and inflection points on its graph effortlessly. Here’s how graphing utilities can aid our process:
- Plot the function using a graphing tool.
- Visually identify critical points where the slope of the tangent is zero (peaks and troughs).
- Spot inflection points where the graph changes concavity.