What am I doing wrong in finding the derivative and max/min?

  • Thread starter randy17
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    Derivative
In summary, when encountering issues with finding expected derivatives, it is important to check for computational errors, discontinuities or incorrect expected values. When dealing with complicated functions, it is helpful to break them down and use rules such as the chain rule, product rule, and quotient rule. To determine if a critical point is a maximum or minimum, the second derivative test can be used. The chain rule can also be applied to implicit functions by rewriting them as explicit functions. To find the absolute maximum or minimum of a function, the Extreme Value Theorem and the first or second derivative test can be used.
  • #1
randy17
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Homework Statement



I need to find the max/min of y=(1)/(3+x^2)

Homework Equations



y=(1)/(3+x^2)

The Attempt at a Solution



I tried to find the derivative; y'= (3+x)^-2(1) = -2(3+x)^-3 = -2/(3+x)^3 or -2/3(3+x)^2?

Whats wrong with it?
 
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  • #2
Well, for starters, the derivative you calculated is wrong. What derivative rule are you using? Your attempt suggests some confusion.
 
  • #3
Start off by using the chain rule (or quotient rule, whichever you prefer) to find the derivative of the function.
 

Related to What am I doing wrong in finding the derivative and max/min?

1. Why do I keep getting a different derivative than what is expected?

There are a few common reasons for this. One possibility is that you may be making a computational error, such as forgetting to apply the chain rule or misplacing a negative sign. Another possibility is that the function you are trying to differentiate is not continuous or differentiable at the point you are interested in. Lastly, it is possible that the expected derivative is incorrect. It is always a good idea to double check your work and consult with a teacher or tutor if you are still unsure.

2. How do I find the derivative of a complicated function?

When dealing with a complicated function, it is important to break it down into smaller, more manageable pieces. Use the chain rule, product rule, and quotient rule as needed. Simplify as much as possible before taking the derivative. It may also be helpful to use tables or graphs to visualize the function and its derivative.

3. How do I determine whether a critical point is a maximum or minimum?

To determine whether a critical point is a maximum or minimum, you can use the second derivative test. Take the second derivative of the function and plug in the critical point. If the resulting value is positive, the critical point is a minimum. If the resulting value is negative, the critical point is a maximum. If the resulting value is zero, the test is inconclusive and you may need to use other methods, such as graphing, to determine the nature of the critical point.

4. Can I use the chain rule to find the derivative of an implicit function?

Yes, you can use the chain rule to find the derivative of an implicit function. First, rewrite the implicit function as an explicit function by solving for the dependent variable. Then, use the chain rule as you normally would for an explicit function. Remember to also apply the chain rule when taking the derivative of the dependent variable with respect to the independent variable.

5. How do I find the absolute maximum or minimum of a function?

To find the absolute maximum or minimum of a function, you can use the first or second derivative test, depending on the function. You can also use the Extreme Value Theorem, which states that a continuous function on a closed interval will have both an absolute maximum and minimum. Set the derivative equal to zero and solve for critical points within the interval, and then evaluate the function at each critical point and at the endpoints of the interval to determine the absolute maximum and minimum.

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