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# Optimization Using the First Derivative Test - Concept

###### Norm Prokup

###### Norm Prokup

**Cornell University**

PhD. in Mathematics

Norm was 4th at the 2004 USA Weightlifting Nationals! He still trains and competes occasionally, despite his busy schedule.

Some optimization problems use the first derivative test to find an absolute minimum or maximum. **Using the first derivative test** requires the derivative of the function to be always negative on one side of a point, zero at the point, and always positive on the other side. Other methods of solving optimization problems include using the closed interval method or the second derivative test.

We have another optimization method we need to study, not every situation is going to land itself to the closed interval method so I want to introduce you to the first derivative test for absolute max and min. Here's the idea behind it, let's say you have a function y equals f of x and the function has a positive derivative to the left of some critical point c and a negative derivative to the right. Well then you can summarize that it has an absolute maximum at c. Now it has to have a positive derivative everywhere to the left and a negative derivative everywhere to the right that will give you an absolute maximum.

This idea is summarizing the first derivative test, suppose f is a differentiable on some interval i and suppose c is the only critical point for f on that interval. If f prime is positive for all x less than c so positive on the left and if it's negative on the right then f will have an absolute maximum and if it's negative on the left and positive on the right it's decreasing and then increasing. It's going to have an absolute minimum at x=c we'll use this method in the next few problems.

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###### Norm Prokup

PhD. in Mathematics, University of Rhode Island

B.S. in Mechanical Engineering, Cornell University

He uses really creative examples for explaining tough concepts and illustrates them perfectly on the whiteboard. It's impossible to get lost during his lessons.

Thiswas EXCELLENT! I am a math teacher and have been looking for an easy/logical way to explain the lateral area of a cone to my students and this was incredibly helpful, thank you very much!”

I just learned more In 3 minutes of polygons here than I do in 3 weeks in my math class”

Hahaha, his examples are the same problems of my math HW!”

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