Ay,A2 =5(-a: Se 63-420] 
or 
= a(— + a1). (6.65) 
This Green’s function is the so—called unit impulse response function that shows the 
response of this physical system to the unit impulse. 
ei ez 
ae) ios 
This impulse response function shows different forms as follows, depending on 
G(t) = (6.66) 
s 
AllV 
ee 
a. When k = 1 (a7 => 4ap), A,A2 are real. Therefore G(r) is a linear combination 
of two exponentials, as is shown in Fig. 6.4. 
Fig. 6.4. G(t) for «21. 
Then 
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