Is This the Correct Approach to Solving Laplace's Equation?

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SUMMARY

The discussion centers on determining whether the function f(x,y) = x^3 + 3xy^2 is a solution to Laplace's equation, uxx + uyy = 0. The initial calculations presented by the user contained errors in the computation of partial derivatives. The correct first derivative is f_x(x,y) = 3x^2 + 3y^2, and the second derivative with respect to x yields the correct result, confirming that the function does not satisfy Laplace's equation. The conclusion is that while the user arrived at the correct result, the methodology and derivative calculations require clarification.

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Homework Statement



Determine whether each of the following functions is a solution of Laplace’s
equation uxx + uyy = 0.

x^3 + 3xy^2

ux=3x^2

uxx=6x

uy=6xy^2

uyy=6x

6x+6x=12x and is therefore not a solution

Did I do that right? I'm just learning about this topic and it's a little hard to understand. Can anyone give any advice as to if I approached this correctly?

 
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while your result is correct, your steps are not written down correctly.
 
Your derivatives are wrong. The procedure is correct, but your partial derivatives are wrong.

You have: [tex]f(x,y)=x^3+3xy^2[/tex]
Then, the derivative with respect to x is:
[tex]f_x(x,y)=3x^2+3y^2[/tex]

Everything else is okey. The result you found is fine because when you take the second derivative with respect to x the term involving y vanishes.
 

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