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Re: How to solve this type of equation in Mathematica?

• To: mathgroup at smc.vnet.net
• Subject: [mg60072] Re: How to solve this type of equation in Mathematica?
• From: spousta at yahoo.com
• Date: Thu, 1 Sep 2005 02:13:08 -0400 (EDT)
• References: <dehk97$cbs$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Hi

try to suppose f(x) in the form

a /(x^3)

for an unknown parameter a

Equal[Integrate[Times[Plus[P, x], Times[a, 1/(x x x)]], List[x, P,
DirectedInfinity[1]]], 1]

Then you get a = 2 P / 3

The same game can be played with another integrable functions - I
suspect you will have too much possible solutions :-)

Greetings

Jan

Jeffrey Lyons wrote:
> Hi, I would like to be able to solve the equation:
>
> Equal[Integrate[Times[Plus[P, x], f[x]], List[x, P,
> DirectedInfinity[1]]], 1]
>
> in Mathematica.  Is there any way to do this?
>
> That is I would like to solve for f(x) when we know that
> integrating  (x + P) f(x) from P to Infinity over x equals 1.