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
Apple to unveil 'iWatch' on September 9
NASA deep-space rocket, SLS, to launch in 2018
Study examines 13,000-year-old nanodiamonds from multiple locations across three continents