Implicit differentiation help (Getting right answer, wrong signs)

rsjrv99

New member
Joined
Nov 18, 2014
Messages
2
This should be simple. I keep getting the right answer but the wrong signs for almost every problem I do. I have evaluated every problem extensively and can't figure out how they are getting different signs for their answers in comparison to mine.

Here is an example problem, I hope it is clear enough. The added in paint brush is just to show you the cancelling out there that I forgot to add. I used the product rule and the chain rule here

c4AoBXQ.jpg
 
This should be simple. I keep getting the right answer but the wrong signs for almost every problem I do. I have evaluated every problem extensively and can't figure out how they are getting different signs for their answers in comparison to mine.

Here is an example problem, I hope it is clear enough. The added in paint brush is just to show you the cancelling out there that I forgot to add. I used the product rule and the chain rule here

View attachment 4652
Those are the same answers.
x (1y2)y (x21) = x (1y2)y (x21)(1)(1) = x (1y2) (1)y (x21) (1) = x (y21)y (1x2)\displaystyle \dfrac{x\space (1 - y^2)}{y\space (x^2 - 1)}\space =\space \dfrac{x\space (1 - y^2)}{y\space (x^2 - 1)} \dfrac{(-1)}{(-1)}\space =\space \dfrac{x\space (1 - y^2)\space (-1)}{y\space (x^2 - 1)\space (-1)}\space =\space \dfrac{x\space ( y^2 - 1)}{y\space (1 - x^2)}
 
Last edited:
Those are the same answers.

So this derivative can have both a positive and negative value referring to two parts of the function at a given x value?

Like a circle, upper semicircle value is positive, while bottom semicircle is negative...


I saw your edit just now, that makes sense and what I was attempting, but for whatever reason I was thinking -1/-1 was -1 which would change sign on the other half of the equation...

OH THE SIMPLE MISTAKES OF MATH!

Thank you!
 
Top