       Re: Manipulation of equations and inequalities in "high-school style"

• To: mathgroup at smc.vnet.net
• Subject: [mg19574] Re: Manipulation of equations and inequalities in "high-school style"
• From: hanson.nospam at physics.auburn.edu (James D Hanson)
• Date: Wed, 1 Sep 1999 23:07:06 -0400
• Organization: Auburn University Physics
• References: <7q9hdf\$o62@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```In article <7q9hdf\$o62 at smc.vnet.net>, silvano at iprolink.ch (Silvano
D'Orazio) wrote:

> Does anybody know a Mathematica (3 or 4) package which allows
> manipulaton of equations and inequalities like high-school students
> are supposed to do?
>
> For example
>
> 2x+a = x-b      subtract a
>   2x = x-b-a    divide by 2, subtract x
>    x = -b-a
>
> or
>
>  (2^x-1)^(1/2) = 5b                 log both sides
> (1/2)(x-1)log2 = log5 + logb        multiply by 2, divide by log2
>
>
>                  2(log5 + logb)     add 1
>            x-1 = --------------
>                      log2
>
> and so on.
>
> I think I saw such a notebook or package some years ago, but I am not
> able to find it any more.
> I think I am not the only teacher who would find this very useful.
> Thanks for all hints.
>
> Silvano D'Orazio
>
>
>
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Three extra bits you need, == instead of = for equations; Map to do
something to both sides of the equation; and functions (the things you
actually do).

In:= ? Map

"Map[f, expr] or f /@ expr applies f to each element on the first level in \
expr. Map[f, expr, levelspec] applies f to parts of expr specified by \
levelspec."

In:= eq1 = (2 x + a == x - b)

Out= a+2 x==-b+x

In:= eq2 = Map[#-a &,eq1]

Out= 2 x==-a-b+x

In:= eq3 = Map[#-x &,eq2]

Out= x==-a-b

--
James D. Hanson                      ph. (334) 844-5044
Department of Physics                fax (334) 844-4613
206 Allison Laboratory
Auburn University, AL 36849-5311     hanson.nospam at physics.auburn.edu

```

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