Laplacian Problem

Shadow · **Posted:** Tue, 1 Nov 2011 00:37:43 UTC

Spartan95 wrote:

$\begin{document} Given u(r,t)$=$Ct$^{\mathrm{-a\thinspace +\thinspace mb}}$ r$^{\mathrm{-m}}$ thus u$^{\mathrm{g}} \quad =$C$^{\mathrm{g}}$ t$^{\mathrm{(-a\thinspace +\thinspace mb)g}}$ r$^{\mathrm{-mg}}$ I am getting: Lapl u$^{\mathrm{g}} \quad =$C$^{\mathrm{g}}$ t$^{\mathrm{(-a+mb)\thinspace g}}$ [(-mg)(-mg-1)] r$^{\mathrm{-mg-2}}$ The correct answer is: Lapl u$^{\mathrm{g}} \quad =$C$^{\mathrm{g}}$ t$^{\mathrm{(-a+mb)\thinspace g}}$ [(-mg)(-mg-1) $+$ (n-1)(-mg)] r$^{\mathrm{-mg-2}}$ Can you help make clear what I am not understanding about the Laplacian that is causing me to loose the (n-1)(-mg)? Thanks! \end{document}$

It's impossible to tell unless you show us how you got there. You could have just forgotten it from the get-go, or lost it somewhere in the middle. Post your work and we should be able to find the problem

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Laplacian Problem

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