View Single Post
Jan30-12, 08:47 PM
P: 93
1. The problem statement, all variables and given/known data

Find the function satisfying the differential equation:

dy/dx - 3y = 6e^(5x)

with y(0) = -6

2. Relevant equations

I believe this is Linear, so it is dy/dx + P(x)y = f(x)

3. The attempt at a solution

I chose -3y to be P and used it to obtain integrating factor e^(-3x). I multiplied it though and ended up with d/dx(e^(-3x)y) = 6e^(2x)

I integrated both sides and got e^(-3x)y = 3e^2x + C

Solving for C gets me -9 so the satisfying function is y=e^(3x)(3e^(2x)-9)

When I try to input this function into Webwork (online homework), it tells me it is incorrect and that the variable 'x' is not defined in this context.

I wanted to make sure I am correct or if somehow, x comes out of this equation.
Phys.Org News Partner Science news on
Security CTO to detail Android Fake ID flaw at Black Hat
Huge waves measured for first time in Arctic Ocean
Mysterious molecules in space