490 

 then 



fi L_- 



-1) 5(>-l) 2 

 and 



1 _V 



7(^17" 7V 



JL4-JL 



# 3 "*" a? 4 

 ! 3 



whence we get by addition, 



c= L_/i__L L_ _id_ ..I, (2 ) 



/ 1\ I ^ 3 f> a ^ ^ 7-n 3 I * * 



f^; 1) t 5 '* o<* otwt'fm J 



The law of the coefficients may be discovered by induction, but is 

 not easily demonstrated in this manner. It may be obtained as 

 follows : 



We have by differentiation 



dc= ^ = ~~^ < 3 > 



Assume 



then 



or 



and by equating coefficients, 



