Re: Algebraic Expression Manipulation

I forgot to mention that since a Constant can be anything, I picked 0.

FullSimplify[Reduce[equ == (-1)^y, {x, y}]] /.
C[1] -> 0

x + y == 1 || x + y == 2

--
HTH. :>)

Dana DeLouis

"Dana" <ddelouis@xxxxxxxxxxxxx> wrote in message
news:nHvfg.524$ED2.66@xxxxxxxxxxxxxxxxxxxxxxxxx
I need a way to take an expression like
(-1)^(2x + 3 y) and be able to reduce it to (-1)^y.

Hi. I'm using v5.2

equ = (-1)^(2*x + 3*y);

Assuming[x + y == 1, FullSimplify[equ]]

(-1)^y

I got the hint from using "Reduce."

FullSimplify[Reduce[equ == (-1)^y, {x, y}]];

--
HTH. :>)
Dana DeLouis


"duli" <dulipishi@xxxxxxxxx> wrote in message
news:1149107746.028317.232890@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
My original post left out the requirement that x,y are integers. With
this requirement, it is possible to simplify since the exponent
is a polynomial in GF(2).

So I need to add that requirement. But even when I specify that,
Mathematica
does not seem to be able to simplify to the required form. Perhaps
I am doing something wrong.


Dave (from the UK) wrote:
duli wrote:
Hello:

I posted this to the mathematica newgroup but somehow it never
appeared. So
I am positing it here.

As someone said it is moderated. Looking at the content of your post, I
don't think Steve would censor it. However, the delays are really
annoying. I give up and don't bother posting there any more.

I need a way to take an expression like
(-1)^(2x + 3 y) and be able to reduce it to (-1)^y.

In general that is simply not true, but of couse it will be under some
circumstances. What do you know about x and y?

I could not figure out how to do this in Mathematica and need
suggestions
as to how one might go about doing this in other packages (like
Maple).

Well, it is simply not possible.


--
Dave K MCSE.

MCSE = Minefield Consultant and Solitaire Expert.

Please note my email address changes periodically to avoid spam.
It is always of the form: month-year@domain. Hitting reply will work
for a couple of months only. Later set it manually.

http://witm.sourceforge.net/ (Web based Mathematica frontend)





.

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