Re: Simplifying with positive constants

• To: mathgroup at smc.vnet.net
• Subject: [mg26079] Re: [mg26062] Simplifying with positive constants
• From: Matt.Johnson at autolivasp.com
• Date: Tue, 28 Nov 2000 01:55:27 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```You just need to specify some assumptions for Simplify or FullSimplify to
use:

In[10]:=
Simplify[1/2(r*a - a*d - Sqrt[4*r*a^2*d + (-r*a + a*d)^2]),
a > 0 && r > 0 && d > 0]
Out[10]=
-a d

-matt

djago at my-deja.com on 11/21/2000 11:55:51 PM

cc:
Subject: [mg26079]  [mg26062] Simplifying with positive constants

I'm trying to calculate some results and when I evaluate them I get:
1/2(r*a-a*d-Sqrt[4*r*a^2*d+(-r*a+a*d)^2]

I know that this is a complicated way of saying:
r*a

but Mathematica (3.0) doesn't seems to get the idea...

I've tried with FullSimplify and so on... but Mathematica won't let a
go out of the Sqrt function. Maybe If I could tell Mathematica that a,
r and d are real and positive values...

Can somebody give me a hint of how to do this???

Thx!

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