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Re: Formula simplify for Solve

• To: mathgroup at smc.vnet.net
• Subject: [mg81005] Re: Formula simplify for Solve
• From: dh <dh at metrohm.ch>
• Date: Fri, 7 Sep 2007 02:13:16 -0400 (EDT)
• References: <fblig0$opg$1@smc.vnet.net>

Hi Lea,

Equality is written by two equal (==) and assignments by one (=). 

Therefore , you can assign an equality to a variable like:

equ=PB2==(A[[2]]*D)+(A[[3]]*B[[1]]+A[[5]]*D)+(A[[3]]*B[[1]]+A[[2]]*B[[2]]+A[[1]]*

D)+(A[[2]]*B[[1]]+A[[3]]*B[[6]]+A[[2]]*B[[3]]+A[[1]]*D)+(A[[5]]*B[[1]]+A[[4]

]*B[[7]]+A[[3]]*B[[3]]+A[[2]]*B[[4]]+A[[1]]*D)

you can then use Solve or Reduce like:

Solve[equ,D]

Note that this only works if A and B are vectors whose elements have 

values (e.g. numeric). Otherwise the statement A[[1]]] failes because 

there is no such element. If you want to work symbliocally, you would 

use A[1] instead of A[[1]]

hope this helps, Daniel



Lea Rebanks wrote:

> Formula simplify for Solve

>  

> PB2=(A[[2]]*D)+(A[[3]]*B[[1]]+A[[5]]*D)+(A[[3]]*B[[1]]+A[[2]]*B[[2]]+A[[1]]*

> D)+(A[[2]]*B[[1]]+A[[3]]*B[[6]]+A[[2]]*B[[3]]+A[[1]]*D)+(A[[5]]*B[[1]]+A[[4]

> ]*B[[7]]+A[[3]]*B[[3]]+A[[2]]*B[[4]]+A[[1]]*D)

> 

> 

> Hi there,

> 

> Please look at the above math statement. I want to incorporate very long

> statements into long formulas & then solve for  D  - is there anyway of

> abbreviating the above statement to a simple letter(s) like PB2 & then be

> able to still solve for  D? I am sure you can - please show me how with

> Mathematia example.

> 

> BTW - I am using version 5.1.0.0 on a PC

> 

> Many thanks for your attention.

> Mr.Lea Rebanks.

> 

>