Show system of PDEs has no solution

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Homework Statement


Show that there is no solution for the system
u_x - 2.999999x^2 y + y = 0,
u_y - x^3 + x = 0.


Homework Equations





The Attempt at a Solution


I took the first equation and integrated w.r.t x, then differentiated w.r.t y. But I'm not sure if it helps:
u_y - \frac{2.999999}{3}x^3 + x = f'(y) where f(y) is an arbitrary function of y.
 
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perishingtardi said:

Homework Statement


Show that there is no solution for the system
u_x - 2.999999x^2 y + y = 0,
u_y - x^3 + x = 0.


Homework Equations





The Attempt at a Solution


I took the first equation and integrated w.r.t x, then differentiated w.r.t y. But I'm not sure if it helps:
u_y - \frac{2.999999}{3}x^3 + x = f'(y) where f(y) is an arbitrary function of y.

And can you choose f(y) such that u_y - x^3 + x = 0, as required?
 
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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