2nd order linear differential equation

Hi, can anyone tell me why this is wrong?

First I factor the characteristic equation and get that r is either 0 or -1:
Attachment 20458

Then I plug those values into the solution for two real roots:

Attachment 20459

But according to wolfram the second term is supposed to be negative. Why is that?

Because Wolfram Alpha is stupid? Since can be positive or negative, it can absorb the negative.

Haha! That makes sense. Thanks