- #1

s3a

- 818

- 8

## Homework Statement

__The problem__:

y''' + 8y = 2x - 5 + 8 e^(-2x); y(0) = -5, y'(0) = 3, y''(0) = -4

__Correct answer__:

y = -23/12 e^(-2x) + e^x (-59/24 cos(sqrt(3) x) + 17 sqrt(3)/72 sin(sqrt(3) x)) + 1/4 x - 5/8 + 2/3 x e^(-2x)

## Homework Equations

Method of undetermined coefficients.

## The Attempt at a Solution

My work is attached as the TheProblemAndMyWork.pdf file. The work is typed (not handwritten), so it looks nice.

What I'm having trouble with is finding the values for c_1, c_2 and c_3. I entered the system of equations from my work into Wolfram Alpha, and the answer is wrong! I re-did this problem so many times, and I keep ending up in the same situation. I suppose, I keep making the exact same mistake.

Could someone please tell me what I am doing wrong?

Any help would be GREATLY appreciated!