- #1

Ortix

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- 0

## Homework Statement

The equation that has to be solved:

y'' - y' - 2y = 2e^(-t)

The problem I am having is that I don't understand why they equatate that part with the derivatives of the u parameters to 0. (see image)

Here they first find the characteristic equation and write down the general solution. They then replace the constants with the parameter "u" and take the derivate.

As you can see, they just say that the derivate part of the u parameter is equal to 0. But why? How? Where did that come from? I can't find it anywhere in my book.

It's probably a facepalm answer but I would really appreciate it