What Is the Correct Solution to the Differential Equation xy'^2 + yy' = 0?

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The correct solutions to the differential equation xy'^2 + yy' = 0 are C1 = y and C2 = xy. The discussion clarifies that the equation can be factored into y'(xy' + y) = 0, leading to y' = 0, which results in y = C1. The alternative solution involves separating variables, yielding y' = -y/x, which integrates to y = -y ln x + C2. The error identified was treating y as a constant during integration.

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xy'^2 + yy' = 0 where y' = dy/dx

The answer is C1 = y and C2 = xy but I get this:

y'(xy' + y) = 0 where y' = 0 and thus y = C1

For the other solution:
xy' + y = 0
y' = -y/x
y = -y ln x + C2
C2 = y + y ln x

Full question is here: http://www.cramster.com/solution/solution/640396
 
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geft said:
y' = -y/x
y = -y ln x + C2

You can't take the antiderivative of that expression because y is a function of x but you've treated y as a constant.

Try get the x and dx on one side, and the y and dy on the other, then integrate.
 
Ah, I see my mistake now. Thanks!
 

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