What Points on y=1/x Have a Tangent Line Slope of -4/9?

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Homework Help Overview

The discussion revolves around finding points on the graph of the function y = 1/x where the slope of the tangent line is -4/9. Participants are exploring the relationship between the derivative of the function and the slope of a given line.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to determine the derivative of the function y = 1/x and relate it to the slope of the line represented by the equation 4x + 9y = 3. Questions about the next steps after finding the derivative are also raised.

Discussion Status

The discussion is ongoing, with some participants providing information about the derivative and its significance in relation to the slope of the tangent line. There is a focus on identifying the specific x-values where the derivative equals -4/9.

Contextual Notes

Participants express confusion about the problem setup and the steps needed to progress, indicating a need for clarification on the relationship between derivatives and tangent slopes.

joshb110
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I'm royally confused... don't even know where to start..

Find the point(s) on the graph of y = 1/x where the tangent line is parallel to 4x + 9y = 3. The m of 4x + 9y = 3 is -4/9 and sadly, that's all i know...
 
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can someone please help me?
 
joshb110 said:
can someone please help me?
First of all, what is the derivative of 1/x. Do you know how to calculate this? Remember that the derivative at some point x0 is the slope of the graph at that point.
 
hi. the derivative of 1/x = -1/ x^2, i believe.
 
what do i do next? do i just graph the two equations?
 
You mean as opposed to actually answering the question??

The problem, as you posted it, "Find the point(s) on the graph of y = 1/x where the tangent line is parallel to 4x + 9y = 3."

You know that the slope of 4x+ 9y= 3 is -4/9, you know that the derivative of y= 1/x at any x is y'= -1/x2 and you know, because apmcavoy just told you, that the derivative at a point is the slope of the tangent line there. For what x is the derivative equal to -4/9?
 

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