By the way the fourier transform works. It is also an exponential function. FourierTransform[g'[x], t, w] g[x] is Also a function of x not t

Sqrt[2 [Pi]] DiracDelta[w] ][g]'[x] The g'[x] is still there and If you can remember the defination of the diracdelta function, this is right and still leaves the g'[x]

I was trying to get an answer similar to this one for the laplace transform. Only the dirac delta would be the laplace transform.

Thanks to both of you, Have a good day

Thanks I will learn how to post this. I started to realize that in order to explain this one I have a bigger problem than just mathematica. I think the person would also have to understand green's functions. I can do them by hand but not with Mathematica and the answer to the problem is easy if you understand green's functions. I do not know if I should go to the mathematics site or the physics site. You have f'[x]e^xs, you can get f[x] by integration by parts. It puts the derivative with respect to x on the e^sx and you get f[x] by itself. So you get -sf[x]e^xs so you now have f[x] by itself, with no derivatives on it. If you have f'[x]e^ys you cannot do an integration by parts, since the derivative of e^ys with respect to x is zero. So the laplace transform e^ys just stays there. If I can get someone to understand this is where the problem is, maybe they can help me. Mathematica should leave it alone, since you do not want to do a integration by parts, which gives 0. But it leaves (f'[x]e^ys)/s...[I will call a] and it is a problem with mathematica I do not understand. In other-words you have done nothing to the function or the exponential but mathematica puts in 1/s and nothing has been done to that part of the equation. David can you lead me in the right direction. It is like asking mathematica not to take a derivative by it gives and extra x or what ever variable.

However, if I read your post correctly, I think LaplaceTransform is working correctly, in that the Laplace transform of 1 is 1/s.

In[1]:= LaplaceTransform[g'[t], t, s]

Out[1]= -g[0] + s LaplaceTransform[g[t], t, s]

In[2]:= LaplaceTransform[g'[x], t, s]

Out[2]= Derivative[1][g][x]/s

In[3]:= LaplaceTransform[1, t, s]

Out[3]= 1/s

Thank's anyway, I really appreciate you trying to help.

I understand that. That is not the problem. Let me put it a little better. When you plug in the Laplace Transform you have to do a integration by parts, to take the derivative of the Laplace transform and get the derivative off the Laplace transform. That would bring down one s variable. It should not do anything but add the Laplace transform to the variable g[x]. g''[t] - g''[x] = DiracDelta[x]*DiracDelta[t], taking the laplace transform would give G''[x] - s^2G = DiracDelta[x]e^-st .where G is now the Laplace transform. Notice nothing happened to the first term G''[x] since we took the Laplace transform with respect to t. It is now LaplaceTransorm/dx^2, the second term changed since it is a function of t and the DiracDelta of t changed because it is a function of t. I cannot write it out better because I do not know what format of this editor. It is not a matter of a dummy variable. It is like taking the partial derivative of xy with respect to x, which gives y.