**S3.**

Let’s start to write the F(s) function by the following way:

Let’s execute the partial fraction operation as follow!

Let's substitute in the equation value! Parameter will be then determined.

Next step: let’s substitute into the same equation for obtaining parameter :

Let’s substitute into the same equation in order to get parameter !

Let’s write A_{3}, B and C into the equation

where only and are unknown. and will be determined by the following way. First , then will be substituted in the equation obtaining the following set of two linear equations for and .

Let’ substitute the two equation :

Consequently

Now all the coefficients of the partial fraction are known, and Laplace transformation can be executed.