Finding local maximums and minimums

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Homework Help Overview

The discussion revolves around finding a cubic function defined as g(x)=ax^3 +bx^2 +cx +d, which has specific local maximum and minimum values at given points. The problem is situated within the context of calculus, particularly focusing on critical points and derivatives.

Discussion Character

  • Exploratory, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to find the derivative of the cubic function and set it to zero but expresses uncertainty about the next steps. Participants suggest establishing equations based on the function's values and its derivative at specified points.

Discussion Status

Participants are actively engaging with the problem, with one suggesting a method to derive four equations from the conditions provided. There is a sense of progress as the original poster acknowledges the guidance but still seeks clarity on the application of the suggested approach.

Contextual Notes

Participants note the need for constraints on the coefficients a, b, c, and d to solve the system of equations effectively. The discussion highlights the importance of correctly interpreting the conditions given in the problem statement.

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Homework Statement


Find a cubic function g(x)=ax^3 +bx^2 +cx +d that has a local maximum value of 2 at -9, and a local minimum value of -7 at 8.


Homework Equations





The Attempt at a Solution


I thought i would find the derivative and set it equal to zero, but i do not know what to do from there
 
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Well, to find the values of a,b,c,d you'll need some constraints on those numbers

1) You know that when you plug 2 in your poly, you should get -9. When you plug -7 in, you would get 8. These deliver two equations.

2) When you derive your function, you know that when you plug 2 in, you get 0. When you plug -7 in, you would get 0 to. These deliver another two equations.

So you have 4 equations. You should be able to solve this system without problems...
 
So plug those numbers in for x? correct?
 
yes!
 
Awesome. i don't know why i didnt get that
 

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