simple PDF

*To*: mathgroup at smc.vnet.net*Subject*: [mg7269] simple PDF*From*: "Lidar (Hamburger) dani" <dani at fh.huji.ac.il>*Date*: Tue, 20 May 1997 02:59:23 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Hello group, I have two questions: 1. Why doesn't MMa 3.0 solve the following simple PDF (at least on my SGI): DSolve[ y^2 D[ g[x,y], {y,2} ] == 2D[ g[x,y], {x,1} ], g[x,y], {x,y} ] nor: <<Calculus`DSolveIntegrals` CompleteIntegral[ y^2 Derivative[0,2][h][x,y] == 2Derivative[1,0][h][x,y], h[x,y], {x,y} ] You can check that a solution is: g[x,y]:=a(Log[y]-x/2)+b y+c 2. How can I force MMa to simplify the following expression: D[ Sum[ (-y)^k/k! f[k], {k,1,Infinity}], {y,1} ] As simplified result I would expect to get: -Sum[ (-y)^(k-1)/(k-1)! f[k], {k,1,Infinity}] Please respond directly to dani at espresso.fh.huji.ac.il Thanks in advance, -- Daniel Lidar Physics Department and Fritz Haber Center for Molecular Dynamics, Hebrew University of Jerusalem, Jerusalem 91904, Israel URL: http://www.fh.huji.ac.il/~dani