expressing a matlab statement

[Dr Preyesh T. Goven Shiba]

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Hi

 

I'm a beginner with the use of matlab and octave... Can someone please help me....How do i express the function y as a amtlab statement for the following expression

 

 

y^2 - 2y = x + 1

 

Thankx

Preyesh

 

Email: drgovenshiba@...

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[dastew]

Dr Preyesh T. Goven Shiba wrote:

> Hi
>  
> I'm a beginner with the use of matlab and octave... Can someone please
> help me....How do i express the function y as a amtlab statement for
> the following expression
>  
>  
> y^2 - 2y = x + 1
>  
> Thankx
> Preyesh
>  
> Email: drgovenshiba@... <mailto:drgovenshiba@...>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Help-octave mailing list
> Help-octave@...
> https://www.cae.wisc.edu/mailman/listinfo/help-octave
>  

I assume that x is the independent variable.
This is a quadratic in y , therefore there are two solutions  for y
y^2 -2y -x-1=0
y= (-b +- sqrt(b^2 -4ac)) /2a      the generic solution.


y1=(2+sqrt(4-4*(-x-1)))/2
or y1=1+sqrt(2+x)
and y2=1-sqrt(2+x)

hope this helps.


 
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[Rolf Fabian]

Dr Preyesh T. Goven Shiba wrote:

Hi

I'm a beginner with the use of matlab and octave... Can someone please help me....How do i express the function y as a amtlab statement for the following expression


y^2 - 2y = x + 1

Thankx
Preyesh

Email: [e-mail]

First, solve the quadratic equation in varible y
"y^2 - 2*y -(x+1) = 0"
using standard school math
and you'll get
y = ... (you should do it by yourself!)

Then, at the Octave prompt, type:
:> function y = myfunc(x) y = .... (your result from above); endfunction

afterwards, you're able to type e.g

[Ben Abbott]

On Mar 6, 2008, at 4:47 AM, Dr Preyesh T. Goven Shiba wrote:

> Hi
>
> I'm a beginner with the use of matlab and octave... Can someone  
> please help me....How do i express the function y as a amtlab  
> statement for the following expression
>
>
> y^2 - 2y = x + 1
>
> Thankx
> Preyesh

Matlab/Octave are computational applications. Assuming I got the  
algebra correct,

y1 = 1 + sqrt(1 + 4*(1+x));
y2 = 1 - sqrt(1 + 4*(1+x));
y = union(y1,y2);

If  you're looking for a program that will provide a symbolic solution  
(i.e. start with y^2-2y=x+1 and provide an equation representing y),  
take a look at Maxima.

http://maxima.sourceforge.net/

Ben


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[Rolf Fabian]

Ben Abbott wrote:

Matlab/Octave are computational applications. Assuming I got the  
algebra correct,

y1 = 1 + sqrt(1 + 4*(1+x));
y2 = 1 - sqrt(1 + 4*(1+x));
y = union(y1,y2);

If  you're looking for a program that will provide a symbolic solution  
(i.e. start with y^2-2y=x+1 and provide an equation representing y),  
take a look at Maxima.

http://maxima.sourceforge.net/

Ben

Ben

IMHO and also from a pedagogical point of view the worst thing to do
is to provide beginners with all-embracing answers.

Fortunately your presented result is that far off from the algebraical
correct result that the questioner still has the chance to improve
his/her calculational skills by solving it alone.

rf