I am trying to understand an example of solving a dif. equation with Laplace. I understand everything except when they add that $+ 1$ on the second line when they are factoring out $X(s)$.
The rearranging the equation obtained for $X(s)$, I got:
$$ \begin{split} sX(s)+X(s)&=3\\ (s+1)X(s)&=3\\ X(s)=&\frac{3}{s+1} \end{split}$$