MATLAB Central Newsreader - root finding of Linear equation

root finding of Linear equation

Eldar — Thu, 29 Oct 2009 09:31:01 -0400

I need to find out the roots of an any linear equation like;
y = ax? + bx? + cx + d
or
y = ax? + bx + c

Any suggestions on how to approach such problem?
Consider that I'm just new user of Matlab.

Re: root finding of Linear equation

John D'Errico — Thu, 29 Oct 2009 10:21:01 -0400

"Eldar " <el_osman@mynet.com> wrote in message <hcbncl$aov$1@fred.mathworks.com>...
> I need to find out the roots of an any linear equation like;
> y = ax? + bx? + cx + d
> or
> y = ax? + bx + c
>
> Any suggestions on how to approach such problem?
> Consider that I'm just new user of Matlab.

In "ax? + bx? + cx + d", what is the ?
supposed to do?

If these were meant to indicate a power
operation, then how is it that you call this
a LINEAR equation? It is nonlinear in the
variable of interest.

In the above case, of course, roots may be
of service to you.

If ? means something else, please explain.

John

Re: root finding of Linear equation

Aprisa — Sat, 21 Nov 2009 03:03:03 -0500

"John D'Errico" <woodchips@rochester.rr.com> wrote in message <hcbqad$3s7$1@fred.mathworks.com>...
> "Eldar " <el_osman@mynet.com> wrote in message <hcbncl$aov$1@fred.mathworks.com>...
> > I need to find out the roots of an any linear equation like;
> > y = ax? + bx? + cx + d
> > or
> > y = ax? + bx + c
> >
> > Any suggestions on how to approach such problem?
> > Consider that I'm just new user of Matlab.
>
> In "ax? + bx? + cx + d", what is the ?
> supposed to do?
>
> If these were meant to indicate a power
> operation, then how is it that you call this
> a LINEAR equation? It is nonlinear in the
> variable of interest.
>
> In the above case, of course, roots may be
> of service to you.
>
> If ? means something else, please explain.
>
> John

Hi John,

I am a new user of Matlab.
how do you find the roots of the function below using Matlab?
f(x)=a(x^2)+b(x)+c

thank you in advance..

Re: root finding of Linear equation

Greg Heath — Sat, 21 Nov 2009 04:27:14 -0500

On Oct 29, 5:21 am, "John D'Errico" <woodch...@rochester.rr.com>
wrote:
> "Eldar " <el_os...@mynet.com> wrote in message <hcbncl$ao...@fred.mathworks.com>...
> > I need to find out the roots of an any linear equation like;
> > y = ax? + bx? + cx + d
> > or
> > y = ax? + bx + c
>
> > Any suggestions on how to approach such problem?
> > Consider that I'm just new user of Matlab.
>
> In "ax? + bx? + cx + d", what is the ?
> supposed to do?
>
> If these were meant to indicate a power
> operation, then how is it that you call this
> a LINEAR equation? It is nonlinear in the
> variable of interest.

It's linear in the unknown coefficients which,
given data, can be solved using backslash.

Greg

Re: root finding of Linear equation

John D'Errico — Sat, 21 Nov 2009 09:43:10 -0500

Greg Heath <heath@alumni.brown.edu> wrote in message <727cae84-3988-4ae8-aaa7-cc73d80056e3@m33g2000vbi.googlegroups.com>...
> On Oct 29, 5:21?am, "John D'Errico" <woodch...@rochester.rr.com>
> wrote:
> > "Eldar " <el_os...@mynet.com> wrote in message <hcbncl$ao...@fred.mathworks.com>...
> > > I need to find out the roots of an any linear equation like;
> > > y = ax? + bx? + cx + d
> > > or
> > > y = ax? + bx + c
> >
> > > Any suggestions on how to approach such problem?
> > > Consider that I'm just new user of Matlab.
> >
> > In "ax? + bx? + cx + d", what is the ?
> > supposed to do?
> >
> > If these were meant to indicate a power
> > operation, then how is it that you call this
> > a LINEAR equation? It is nonlinear in the
> > variable of interest.
>
> It's linear in the unknown coefficients which,
> given data, can be solved using backslash.
>
> Greg

NO. You can solve for the coefficients using
backslash.

But you cannot solve for the roots of an equation
using backslash!

You can use fzero to find a root, or roots to find
the roots if the equation is quadratic, as it appears
to be.

John

Re: root finding of Linear equation

John D'Errico — Sat, 21 Nov 2009 09:44:05 -0500

"Aprisa " <aprisamd@gmail.com> wrote in message <he7l97$34m$1@fred.mathworks.com>...
> "John D'Errico" <woodchips@rochester.rr.com> wrote in message <hcbqad$3s7$1@fred.mathworks.com>...
> > "Eldar " <el_osman@mynet.com> wrote in message <hcbncl$aov$1@fred.mathworks.com>...
> > > I need to find out the roots of an any linear equation like;
> > > y = ax? + bx? + cx + d
> > > or
> > > y = ax? + bx + c
> > >
> > > Any suggestions on how to approach such problem?
> > > Consider that I'm just new user of Matlab.
> >
> > In "ax? + bx? + cx + d", what is the ?
> > supposed to do?
> >
> > If these were meant to indicate a power
> > operation, then how is it that you call this
> > a LINEAR equation? It is nonlinear in the
> > variable of interest.
> >
> > In the above case, of course, roots may be
> > of service to you.
> >
> > If ? means something else, please explain.
> >
> > John
>
> Hi John,
>
> I am a new user of Matlab.
> how do you find the roots of the function below using Matlab?
> f(x)=a(x^2)+b(x)+c
>
> thank you in advance..

Use roots. This is what it does. fzero will also
find a root, but only one root at a time.

John

Re: root finding of Linear equation

Greg Heath — Sat, 21 Nov 2009 18:27:01 -0500

On Nov 21, 4:43 am, "John D'Errico" <woodch...@rochester.rr.com>
wrote:
> Greg Heath <he...@alumni.brown.edu> wrote in message <727cae84-3988-4ae8-aaa7-cc73d8005...@m33g2000vbi.googlegroups.com>...
> > On Oct 29, 5:21?am, "John D'Errico" <woodch...@rochester.rr.com>
> > wrote:
> > > "Eldar " <el_os...@mynet.com> wrote in message <hcbncl$ao...@fred.mathworks.com>...
> > > > I need to find out the roots of an any linear equation like;
> > > > y = ax? + bx? + cx + d
> > > > or
> > > > y = ax? + bx + c
>
> > > > Any suggestions on how to approach such problem?
> > > > Consider that I'm just new user of Matlab.
>
> > > In "ax? + bx? + cx + d", what is the ?
> > > supposed to do?
>
> > > If these were meant to indicate a power
> > > operation, then how is it that you call this
> > > a LINEAR equation? It is nonlinear in the
> > > variable of interest.
>
> > It's linear in the unknown coefficients which,
> > given data, can be solved using backslash.
>
> > Greg
>
> NO. You can solve for the coefficients using
> backslash.
>
> But you cannot solve for the roots of an equation
> using backslash!

John, please splash your face with water.
I said given data, not given coefficients.

Greg