Find closed loop transfer function from the open loop transfer function for a unity feedback

Problem: Given

\[ L(s)=\frac {s}{(s+4)(s+5)}\]

as the open loop transfer function, how to ﬁnd \(G(s)\), the closed loop transfer function for a unity feedback?

Mathematica

Clear["Global`*"]; 
sys = TransferFunctionModel[ 
             s/((s+4)(s+5)),s]

pict

closedLoop = SystemsModelFeedbackConnect[sys];

pict

The system wrapper can be removed in order to obtain the rational polynomial expression as follows

First[Flatten[closedLoop[[1,1]]/ 
         closedLoop[[1,2]]]]

\[ \frac {s}{s^2+10 s+20} \]

Matlab

clear all; close all; 
s=tf('s'); 
sys=s/((s+4)*(s+5)); 
closedloop=feedback(sys,1)

Transfer function: 
       s 
--------------- 
s^2 + 10 s + 20