Partial fraction method (in s-space)

The following is a part of a current **I(s)** (in $\displaystyle s$-space):

http://img191.imageshack.us/img191/4021/giflatex2.gif

What am I doing wrong in using this formula for finding $\displaystyle A$ and $\displaystyle B$:

http://img546.imageshack.us/img546/4265/giflatex3.gif ; where $\displaystyle a$ is a pole.

PROBLEM

I easily find **A**, but not **B**:

http://img269.imageshack.us/img269/7302/giflatex4.gif

end of PROBLEM

The solution (which is correct) is http://img251.imageshack.us/img251/315/giflatex5q.gif

What am I doing wrong inside the PROBLEM section? Or is the formula for $\displaystyle A$ (or $\displaystyle B$) wrong? (Crying)