Identifying Horizontal Tangents on the Graph of y = x^3e^x

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Homework Help Overview

The discussion revolves around identifying points on the graph of the function y = x3ex where the tangent line is horizontal. Participants are exploring the application of the product rule in calculus to find the derivative and determine the conditions for horizontal tangents.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants attempt to apply the product rule to find the derivative of the function and set it to zero to identify horizontal tangents. There are questions about whether additional solutions exist, particularly regarding the factor of x2.

Discussion Status

The discussion is ongoing, with participants providing feedback on each other's attempts. Some guidance has been offered regarding the identification of points with horizontal tangents, and there is an acknowledgment of the need to consider all factors in the derivative.

Contextual Notes

Participants note uncertainty about the correctness of their calculations and the implications of the factors in the derivative. There is a focus on ensuring that all potential solutions are considered in the context of the problem.

Dustobusto
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Homework Statement



Find the points on the graph of y = x3ex where the tangent line is horizontal.
(Your answer should include x-values and y-values)


Homework Equations



Product rule

fg'+gf'


The Attempt at a Solution



(x3)(ex)+(ex)(3x2)

x3ex+3x2ex= y'

x3ex+3x2ex= 0

x2ex(x+3) = 0

x = -3

Going back to original equation, and plugging in x:

y = -33e-3

y = -27e-3

y ≈-1.34

Not sure if I did this correctly.
 
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Dustobusto said:

Homework Statement



Find the points on the graph of y = x3ex where the tangent line is horizontal.
(Your answer should include x-values and y-values)

Homework Equations



Product rule

fg'+gf'

The Attempt at a Solution



(x3)(ex)+(ex)(3x2)

x3ex+3x2ex= y'

x3ex+3x2ex= 0

x2ex(x+3) = 0

x = -3

Going back to original equation, and plugging in x:

y = -33e-3

y = -27e-3

y ≈-1.34

Not sure if I did this correctly.

Looks fine, but you should provide a summary of what you found - something like this: The only point with a horizontal tangent is (-3, -27e-3), or approximately (-3, -1.34).
 
Mark44 said:
Looks fine, but you should provide a summary of what you found - something like this: The only point with a horizontal tangent is (-3, -27e-3), or approximately (-3, -1.34).

Okay. Also, with

x2ex(x+3) = 0

x = -3 but does it also = 0? Graphing it, it looks like I could include that value as well.
 
Sorry, I overlooked that factor of x2, so yes, your function has a horizontal tangent at (0, 0).
 

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