I think, the purpose of the components should be explained in more detail:
1.) R3 and R6 provide negative feedback for the signals to be amplified. This gives better linearity and increases the input impedance. At the same time the gain is decreased (see contribution from KEITH), but that's the normal price to be paid for better linearity.
2.) (R3+R8) and (R6+R9) provide negative feedback for DC (and very low frequencies) only. This stabilizes the operating point against tolerances and temperature deviations.
---------- Post added at 15:01 ---------- Previous post was at 14:18 ----------
*As far as the last question is concerned:
And i think the total resistance value can be determined at the Transistor's emitter by adding the the resistors value which are in series..Am i right????
The answer is: It depends. For dc feedback purposes both R's act in series. However, for calculating the corner frequency of the feedback high pass (very low frequecies: much feedback/lower gain; higher frequecies: less feedback/higher gain) both resistors have to be considered in parallel.
*One remark to sunny1986's "lapidar" statement "use for stability":
Negative feedback always has two consequences: It enlarges dc operating point stability and - at the same time - it lowers system stability (poorer stability margin) against self-excitement.