Finding Extreme x-Values on a Parabola

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Homework Help Overview

The problem involves finding the coordinates of points on a parabola defined by the equation 9x² + 24xy + 16y² + 20x - 15y = 0 that have extreme x-values. The original poster expresses confusion regarding the meaning of "extreme x-values" and questions how to approach the problem, particularly in relation to the parabola's properties.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the implications of the parabola's orientation and its potential boundedness in the x-direction due to the presence of the "xy" term. The original poster considers implicit differentiation as a method to find extrema but is uncertain about its application. Others suggest differentiating x with respect to y and using implicit differentiation to identify extreme values.

Discussion Status

Some participants have provided guidance on the differentiation process, emphasizing the need to treat x as a function of y. There is an ongoing exploration of the implications of the derivative and how to find points corresponding to x maxima and minima. The discussion reflects a mix of interpretations and approaches without reaching a consensus.

Contextual Notes

Participants note that the parabola's axis of symmetry and the presence of the "xy" term may affect its boundedness in both x and y directions. The original poster's understanding of extreme x-values is still under examination.

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Homework Statement



The parabola [tex]9x^{2} + 24xy + 16y^{2} + 20x - 15y = 0[/tex] has vertex at the origin. Find the coordinates of the points on the parabola that have extreme x-values

Homework Equations





The Attempt at a Solution



To start off, I don't quite understand the question. What does it mean for points on a parabola to have an extreme x-value? Don't parabolas extend til infinity in the x-direction? I thought about implicitly differentiating and going after the min/max values using the first derivative, but I don't see how that's going to answer the question. Someone have an idea? Thanks
 
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Parabolas that have axis of symmetry parallel to the y-axis are unbounded in x but not y. Because of the "xy" term, this parabola is at an angle to the axes and may be bounded in both x and y. Since you want to find the "extreme x" values, you want to think of x as a function of y. Differentiate x with respect to y using implicit differentiation.
 
It means find the points on the parabola corresponding to x maxima and minima. One of these is infinite. Go with implicit differentiation and find the points.
 
Thanks guys; I implicitly differentiated and found that [tex]\frac {dx}{dy} = \frac {15 - 32y}{18x + 44}[/tex]. I used this to say that when the denominator is 0, namely when x is -44/18, x is an extreme. Does this sound right?
 
Try doing the differentiation again. Remember you are taking the derivative w.r.t. y, assuming x is a function of y. Please don't forget to use the product rule.
 
Set the derivative to 0 and solve for x or y. Then put back into the original equation to find the points.
 

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