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}]

dani at espresso.fh.huji.ac.il

--
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

```

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