Is it okay to treat dy/dx as a fraction when solving for derivatives?

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In summary, the conversation discusses treating dy/dx as a fraction in certain scenarios and manipulating it algebraically. It also touches on the concept of limits and the rules of derivatives. The conclusion is that there are no rules being violated in this context.
  • #1
Nano-Passion
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Homework Statement


Am I right to treat dy/dx as a fraction in this scenerio?

Homework Equations





The Attempt at a Solution




[tex]= \frac{\frac{-dy}{dx}} {(\frac{dy}{dx})^2}[/tex]
[tex]= \frac{\frac{-dy}{dx}} {\frac{dy}{dx} (\frac{dy}{dx})}[/tex]
[tex]= \frac{1}{\frac{dy}{dx}}[/tex]

Also, would we be able to multiple out dy/dx if we had for example:

[tex] 2 = \frac{1}{\frac{dy}{dx}}[/tex]
[tex] 2(\frac{dy}{dx}) = 1 [/tex]
 
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  • #2
Nano-Passion said:

Homework Statement


Am I right to treat dy/dx as a fraction in this scenerio?
Sure.
Nano-Passion said:

Homework Equations





The Attempt at a Solution




[tex]= \frac{\frac{-dy}{dx}} {(\frac{dy}{dx})^2}[/tex]
[tex]= \frac{\frac{-dy}{dx}} {\frac{dy}{dx} (\frac{dy}{dx})}[/tex]
[tex]= \frac{1}{\frac{dy}{dx}}[/tex]
What happened to the minus sign?

Note that you can simplify 1/(dy/dx).
Nano-Passion said:
Also, would we be able to multiple out dy/dx if we had for example:

[tex] 2 = \frac{1}{\frac{dy}{dx}}[/tex]
[tex] 2(\frac{dy}{dx}) = 1 [/tex]
Sure. And if the goal is to solve for dy/dx, divide both sides of the last equation by 2.
 
  • #3
Mark44 said:
Sure.
What happened to the minus sign?
Simple mis-type.

Note that you can simplify 1/(dy/dx).
Like this?
[tex]=\frac{dx}{dy}[/tex]

Which would read change of x with respect to y.. Hmm, I'm not used to it being like that.

[tex]=\frac{dx}{dy} = lim_{Δx→0} \frac{Δx}{Δy}[/tex]
[tex]= lim_{Δx→0} \frac{Δx}{f(x+Δx) - f(x)}[/tex]
[tex]= f'(y)[/tex]

Is what I stated correct?

Sure. And if the goal is to solve for dy/dx, divide both sides of the last equation by 2.


Oh okay, thank you! I just wanted to make sure I wasn't violating any rules here pertaining to derivatives.
 
Last edited:
  • #4
Nano-Passion said:
Simple mis-type.


Like this?
[tex]=\frac{dx}{dy}[/tex]

Which would read change of x with respect to y.. Hmm, I'm not used to it being like that.

[tex]=\frac{dx}{dy} = lim_{Δx→0} \frac{Δx}{Δy}[/tex]
No, the limit would be as Δy→0. Here the assumption would be that x is some function of y.
Nano-Passion said:
[tex]= lim_{Δx→0} \frac{Δx}{f(x+Δx) - f(x)}[/tex]
[tex]= f'(y)[/tex]

Is what I stated correct?




Oh okay, thank you! I just wanted to make sure I wasn't violating any rules here pertaining to derivatives.
 

1. What is the purpose of dividing dy/dx by (dy/dx)^2?

The purpose of dividing dy/dx by (dy/dx)^2 is to simplify the expression and to eliminate any possible division by zero.

2. Can you divide dy/dx by (dy/dx)^2 if dy/dx is equal to zero?

No, you cannot divide by zero. In this case, the expression is undefined.

3. Is dividing dy/dx by (dy/dx)^2 the same as taking the derivative of dy/dx?

No, dividing dy/dx by (dy/dx)^2 is not the same as taking the derivative. The derivative of dy/dx is equal to (d^2y)/(dx^2).

4. Will dividing dy/dx by (dy/dx)^2 change the value of dy/dx?

No, dividing dy/dx by (dy/dx)^2 will not change the value of dy/dx. It will only simplify the expression.

5. Can you divide dy/dx by (dy/dx)^2 if dy/dx is a complex number?

Yes, you can divide dy/dx by (dy/dx)^2 even if dy/dx is a complex number. The result will also be a complex number.

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