What is the derivative of y with respect to x at the point (2,-3)?

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Homework Help Overview

The problem involves finding the derivative of y with respect to x for the equation y^2 - 2xy = 21 at the point (2, -3). The subject area is calculus, specifically implicit differentiation.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss whether to differentiate implicitly or explicitly and explore both methods. There are attempts to derive dy/dx, with some participants expressing uncertainty about their calculations and the correct manipulation of terms.

Discussion Status

The discussion is ongoing, with participants providing guidance on the differentiation process and questioning the correctness of their approaches. Some participants have identified mistakes in their previous attempts and are reconsidering their steps.

Contextual Notes

Participants are navigating the complexities of implicit differentiation and are addressing errors in their calculations. There is a focus on ensuring that dy/dx is isolated correctly in the equations presented.

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Homework Statement


If y^2 - 2xy=21, then dy/dx at the point (2,-3) is ?


Homework Equations


y^2 - 2xy=21


The Attempt at a Solution


I know that I have to differentiate the function. I just do not know how to do it: implicitly or explicitly.
 
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Why not try both ways?

Actually, you should get the same (correct) answer doing either.)
 
i tried to diff it in terms of dy/dx but I don't think i got it right. i got dy/dx to equal 2y+2x
 
what I did was...
y^2= 2xy +21
2dy/dx=2(y+x(dy/dx))
2(dy/dx)= 2y+2x(dy/dx)
Divide by dy/dx on both sides
dy/dx=2y+2x
 
Never mind, I see what I did wrong. I should have put the two dy/dx's on the same side, take out dy/dx and then just divide to get dy/dx alone.
 
y^2= 2xy +21
2dy/dx=2(y+x(dy/dx))


This step is wrong. It should be
2y*dy/dx = 2(y+x(dy/dx))
 

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