# Non homogeneous 1D heat equation

ut = 3uxx + 2, 0 < x < 4, t > 0,

u(0,t) = 0, u(4,t) = 0, t = 0

u(x,0) = 5sin2πx,0 < x < 4.

(a) Find the steady state solution uE(x)

(b) Find an expression for the solution.

(c) Verify, from the expression of the solution, that limt→∞ u(x, t) = uE (x)

for all x, 0 < x < 4.

https://brainmass.com/math/fourier-analysis/non-homogeneous-heat-equation-624667

#### Solution Preview

The eqaution is:

(1.1)

With boundary condition

(1.2)

And initial conditions

(1.3)

The steady state is, by definition:

(1.4)

The function is now only x-dependent so the partial derivatives become full derivatives and the ordinary differential equation is

(1.5)

And the boundary conditions must still hold:

(1.6)

Integrating (1.5) twice we obtain:

(1.7)

Applying boundary conditions we get the steady state solution.

(1.8)

We would like to turn the system into a homogenous system.

So we write:

(1.9)

When we apply it to the original equation we get:

(1.10)

If we set

(1.11)

the equation becomes homogenous.

For the boundary conditions we ...

#### Solution Summary

The solution contains 10 pages of step by step explanation how to solve the heat equation u_t = u_xx + 2.