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

In summary: So the summary should be: In summary, the points on the graph of y = x3ex where the tangent line is horizontal are (-3, -27e-3) and (0, 0).
  • #1
Dustobusto
32
0

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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  • #2
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).
 
  • #3
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.
 
  • #4
Sorry, I overlooked that factor of x2, so yes, your function has a horizontal tangent at (0, 0).
 

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

How do you find the points on a graph?

To find the points on a graph, you will need to locate the x and y coordinates of each point. You can do this by looking at the axes of the graph and finding where the lines intersect. The x coordinate represents the horizontal position and the y coordinate represents the vertical position of the point.

Why is it important to find the points on a graph?

Finding the points on a graph is important because it allows you to accurately interpret and analyze the data presented in the graph. It also helps you understand the relationship between the variables represented on the graph.

What are some methods for finding points on a graph?

There are a few methods for finding points on a graph, depending on the type of graph. For a line graph, you can use the slope-intercept form (y=mx+b) to find the points. For a scatter plot, you can use a trend line or regression equation to find the points. Additionally, you can use the scale and grid lines on the graph to estimate the points.

Is it possible to find all the points on a graph?

In most cases, it is not possible to find all the points on a graph. This is because there are an infinite number of points between two given points on a graph. However, you can find a close approximation of the points by using the methods mentioned in question 3.

How can I check if my points are accurate?

To check if your points are accurate, you can use them to plot a line or curve on the graph and see if it matches the original data points. You can also use a calculator or software to calculate the values of the data points and compare them to the points on the graph. Additionally, you can use the scale and grid lines on the graph to ensure the points are in the correct location.

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