Review in calc I to prepare for calc II

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Discussion Overview

The discussion revolves around reviewing concepts from calculus I, specifically focusing on optimization techniques involving derivatives in preparation for calculus II. Participants explore methods for determining the nature of critical points in optimization problems.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant inquires about methods to determine which critical point to use when multiple critical points exist in optimization problems.
  • Another participant suggests using the first derivative test, explaining that if the derivative changes from negative to positive at a critical point, it indicates a maximum, while the opposite indicates a minimum.
  • A later reply reiterates the first derivative test and clarifies the conditions for identifying maxima and minima based on the behavior of the derivative around critical points.
  • Another participant proposes using the second derivative test, stating that if the second derivative is negative at a critical point, it indicates a maximum, while a positive value indicates a minimum. They also mention the case when the second derivative is zero, referring to it as a bending point.

Areas of Agreement / Disagreement

Participants present multiple methods for determining the nature of critical points, including both the first and second derivative tests. There is no consensus on which method is preferred, as different participants advocate for different approaches.

Contextual Notes

Some participants assume familiarity with derivative concepts and tests, which may limit understanding for those less experienced. The discussion does not resolve which method is superior or under what conditions each method should be applied.

Who May Find This Useful

Students preparing for calculus II, particularly those reviewing optimization techniques and derivative tests.

ranger
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I'm doing a review in calc I to prepare for calc II. I'm now applications of derivatives (optimization). Okay so when I have the function I need to optimize, I need to take the derivative and find the critical point of the first derivative. But sometimes there's more than one critical point. Is there any sort of test that I can do to find which critical point I should use.

--thank you.
 
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Why not a first derivative test? I assume you have done one before. If the derivative is negative until the critical point, then positive after the critical point then you have a maximum. The other way around for a minimum. Essentially limits with derivatives.
 
Ah the first derivative test. Thanks for the input.
 
Mindscrape said:
Why not a first derivative test? I assume you have done one before. If the derivative is negative until the critical point, then positive after the critical point then you have a maximum. The other way around for a minimum. Essentially limits with derivatives.

Other way around, if the derivative is negative to the critical point and the positive after the value at that point is a minimum, because the function decreases to that point and then increases.
 
You could also get the second derivative and evaluate it in the critical points (where the first derivative is zero). If the second derivative is negative you have a maximum, if it's positive you have a minimim and if it's zero you have (what i directly translate from dutch, because I don't know what it's called in english) a bending point, as you would have in the function y=x^3. If calculating the second derivative isn't too much work, I generally use this method to establish the nature of a critical point.
 

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