# Substitude variables on a array of equations... - Hewlett Packard

This is a discussion on Substitude variables on a array of equations... - Hewlett Packard ; Hi all! I have a function that retuns me a array with two equations... Something like this: [x^2+y X^2-2y] Is there any way that i can use to substitute X and Y by real numbers, like; x=2 and y=1 And ...

# Thread: Substitude variables on a array of equations...

1. ## Substitude variables on a array of equations...

Hi all!

I have a function that retuns me a array with two equations...
Something like this:

[x^2+y X^2-2y]

Is there any way that i can use to substitute X and Y by real numbers,
like;
x=2 and y=1

And get an array with the responses:
[5 2]

Thanks a lot!!!

2. ## Re: Substitude variables on a array of equations...

I'm not a big expert but I would use two mechanisms (in RPN):
1) Give values to variabile (for aproximate result)
[X^2+Y X2-2Y] using Matrix Writer (remember quote ' to input algebric
construct)
2
'X'
STO
1
'Y'
STO
->NUM

3) Use symbolic substitutions (SUBST command in ALG menu)
[X^2+Y X2-2Y] using Matrix Writer
'X=2'
SUBST
'Y=1'
SUBST
EXPAND

There is a | (where) construct but I'm not very able in using it. Pheraps
some newsgroup "gurus" can help us.

MS

3. ## Re: Substitude variables on a array of equations...

On Apr 18, 10:12 am, Regis Daniel
wrote:
> Hi all!
>
> I have a function that retuns me a array with two equations...
> Something like this:
>
> [x^2+y X^2-2y]
>
> Is there any way that i can use to substitute X and Y by real numbers,
> like;
> x=2 and y=1
>
> And get an array with the responses:
> [5 2]
>
> Thanks a lot!!!

HI!

It's very simple.
Create an array with the matrix writer [white button - O (between N
and P)], then press [orange button O (between N and P] to create an
equation within the array, then press x^2+y, ENTER. Then repeat for
the next equation, then ENTER to place the array on the stack. Your
matrix should look like this:
[ 'x^2+y' 'x^2-2*y'] in level 1. Then start a new array (see above),
start equation writer within the array and enter x=2 Enter, eq writer,
y=1, ENTER ENTER.
The stack will now show (if things were done right):
2: ['x^2+y' 'x^2-2*y]
1: [x=2 y=1]
now press: orange-4 (the ALG menu), NXT (to go to page two), press
SUBST, and voila! X and Y will be substituted with the appropriate
values. You will have to edit each element and press EVAL to reduce,
but minor point.

Please note: I assume you are using a 50g. If you don't have one, I
hope you will give serious consideration getting one.

I hope this helps!