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Ch. 4 - Applications of the Derivative
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Not the one you use?Change textbook
Chapter 4, Problem 75

Concavity Determine the intervals on which the following functions are concave up or concave down. Identify any inflection points.


g(t) = 3t⁵ - 30t⁴ + 80t³ + 100

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First, find the first derivative of the function g(t) = 3t⁵ - 30t⁴ + 80t³ + 100. This will help us understand the rate of change of the function.
Next, find the second derivative of the function. The second derivative will help us determine the concavity of the function. Use the first derivative to calculate this.
Set the second derivative equal to zero and solve for t. This will help identify potential inflection points where the concavity might change.
Analyze the sign of the second derivative on the intervals determined by the critical points found in the previous step. If the second derivative is positive, the function is concave up; if negative, concave down.
Identify any inflection points by checking where the second derivative changes sign. These points are where the function transitions from concave up to concave down or vice versa.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Concavity

Concavity refers to the direction in which a curve bends. A function is concave up on an interval if its second derivative is positive, indicating that the slope of the tangent line is increasing. Conversely, a function is concave down if its second derivative is negative, meaning the slope of the tangent line is decreasing. Understanding concavity helps in analyzing the behavior of functions and identifying points of inflection.
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Determining Concavity Given a Function

Second Derivative Test

The second derivative test is a method used to determine the concavity of a function and locate inflection points. By calculating the second derivative of a function, we can assess where it changes sign. If the second derivative is positive, the function is concave up; if negative, it is concave down. Inflection points occur where the second derivative equals zero or is undefined, indicating a change in concavity.
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Inflection Points

Inflection points are specific points on a curve where the concavity changes. These points are found by setting the second derivative equal to zero and solving for the variable. At an inflection point, the function transitions from concave up to concave down or vice versa. Identifying these points is crucial for understanding the overall shape and behavior of the function.
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Critical Points
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