Can Implicit Differentiation Reconstruct the Original Equation?

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Homework Statement


This is just something I am doing for fun. If you see my attachment you will see I took an equation (underlined) and differentiated it implicitly to give me a separable equation (boxed)

How do I solve the separable equation to work backwards to get the underlined equation?

I apologize in advance, I forgot to bring the negative sign into the separable equation.

Homework Equations


in attachment

The Attempt at a Solution


in attachment
 

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shreddinglicks said:

Homework Statement


This is just something I am doing for fun. If you see my attachment you will see I took an equation (underlined) and differentiated it implicitly to give me a separable equation (boxed)

How do I solve the separable equation to work backwards to get the underlined equation?

I apologize in advance, I forgot to bring the negative sign into the separable equation.

Homework Equations


in attachment

The Attempt at a Solution


in attachment
From your attachment, here's what you have:
##y^2 + 2xy = C##
##2y\frac{dy}{dx} + 2y + 2x\frac{dy}{dx} = 0##
##\frac{dy}{dx} 2x + 2y = -2y##
##\frac{dy}{dx} = \frac{-y}{x + y}## (added the minus sign that you mentioned)

The third line needs parentheses around 2x + 2y.
Your final equation is not separable. Another tactic must be used. One that works is to let u = y/x. That will give you a separable DE.
 
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