1. The problem statement, all variables and given/known data

Determine the solution for

when

U(t) is the unit step function

3. The attempt at a solution

Laplacetransforming :

With given data the equation becomes

Solving Y(s)

Transform again:

Problem: This is wrong but I dont know what am I doing wrong..Can someone tell me what Im doing wrong? Wolframalpha.com says that the solution should be:

But I dont understand how to get that answer.

Thanks!!