Ex.2:

a)

$H(s)=3/(s^2+4s+8)$

b)

$H(0)=3/8$; $H(\infty)=0$;

c)

${{d^2e_2}\over {dt^2}}+{{de_2}\over {dt}}-12.5 e_2=-3/2{{de_1} \over {dt}}$