Partial differential equations with laplas

jd1828
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Homework Statement



Solve the partial differential equation using laplas transforms:

U`(x)=a^2*U``(t)

given U(x,0)=2


There are more initial conditions but i am just trying to get to the general solution

The Attempt at a Solution



First take laplas of the equation. Then I am trying to get it into a differential equation form that i know how to solve.

im not sure what method its called but I get

r^2 - s/(a^2)=0

Im not to sure if that is correct.
 
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I should add that after taking the laplas of the equation I get:

S*U(s)-2=a^2*(d^2/dx^2)U(s)
 
solve this using separation of variables in which you assume that u is

u(x,t) = X(x)T(t)

once you substitute this back int othe original equation you can separate that into two second order lienar DEs which you can solve easily.
 
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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