H I S T O I R E. 



109 



r(lf)(^)-(ifV 



PT^ + CfpJ 



dy 



&■:& 



01 



•dy 



+ 



L \ 3x / \ dy /J 



+ (3 / [n'(!£)-t-(f5)] 

 h- a' n (§£) W" : cj/ -+- r(^ru^) — (^) (^)i 



'. n n . 



/' : W 



+ P''n(|f) 



V = 



+'£«$£).-+ (g)i 



+ SK^)(^-)-(^')(|f')]/':r 



+0 



-3. ' 



\dx/ \dy/ 



+ P'[n / (^) + (f^)] 



4-a'n(^e:) 

 +>n(#) 



Egalant a zero les coefllciens de F^-dy. f 



ra«'(||:) + p' ( ^ )=:o •" '; 



<£>", on au- 



« n (^K p n (^) -, #<§*) (§£> - (|^) ( ^ }] = e. 



On 



