Implicit Differentiation Question

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Homework Statement


I am told to find dy/dx by implicit differentiation where:
e^(x^2 * y) = x + y

Homework Equations


The above equation and the ln of it.

The Attempt at a Solution


e^(x^2 * y) = x + y
(x^2 * y)ln(e) = ln(x+y)
x^2 * y = ln(x+y)
x^2(dy/dx) + y(2x) = 1/(x+y) * (1 + dy/dx)
(dy/dx)[x^2 - 1/(x+y)] = 1/(x+y) - 2xy
dy/dx = (1/(x+y) - 2xy)/(x^2 - 1/(x+y))

or here: https://postimg.org/image/3k5ygbkxt/

This was marked wrong (online software). It doesn't care about simplest form and it was entered properly. So, what did I do wrong?
 

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I got the same result without using the logarithm, only with a single quotient, i.e. expanded by ##x+y##. Maybe the missing brackets in your linear notation led to the online error. Or it is expected to write ##e^{x^2y}## instead of ##x+y## in the solution.
 
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fresh_42 said:
I got the same result without using the logarithm, only with a single quotient, i.e. expanded by ##x+y##. Maybe the missing brackets in your linear notation led to the online error. Or it is expected to write ##e^{x^2y}## instead of ##x+y## in the solution.

I just put it in replacing x+y with e^(x^2 * y) and it worked. Thanks!
 
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There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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