SEMAINE D'ÉTUDE SUR LE ROLE DE L’ANALYSE ECONOMETRIQUE ETC. 74 
so that we have 
177-8) 
R_ZR, 8B _, IR, 3Y 
R ER B  =R,Y 
in which the ËR, &B and 8Y correspond to virtual displacements 
compatible with the restraints. 
Now, the conditions for Paretian optimum can be written 
II7-Q) 
Np _ 
5, 
‘Rb a 
YB T 
where a, © 
AB... C 
-, ..., 2 are the prices of the goods 
2). 
Carrying the values of the derivatives of R given by (117-9) 
nto (117-8), we have 
JR YbBB _ 5 LycY 
SCSAB TN 
; À 
f 
!) ALLAIS, Treatise on Pure Economics (1943), p. 204. 
‘111 Allais - pag. 45