Date: Apr 4, 2013 9:20 PM
Author: Nasser Abbasi
Subject: Re: How can I change a variable in a equation when use "solve"?
On 4/4/2013 5:17 PM, Jingzhou Wang wrote:

> Dear all,

>

> A question about using the solve function. My code is as follows,

>

> syms a x y

> s = solve('x*exp(x)=y, y=a-x','x,y')

> s = [s.x s.y]

>

> It works when I use a number such as "2" instead of "a" in the equation

>'y=a-x'. But when I include the variable in the equation, it doesn't go.

>Since I want to change the "a" value outside the "solve" function, how can I do this?

>

> The matlab version is R2010a.

>

> Many thanks!

>

> Jing

>

There is no algebraic solution for x

--------------------

EDU>> syms x y a

EDU>> sol=solve(x*exp(x)==a-x,x)

Warning: Explicit solution could not be found.

> In solve at 179

--------------------

when you put a number for 'a', then matlab must have used

numerical root finding to solve it

EDU>> sol=solve(x*exp(x)==2-x,x)

0.6748316143423993509028640916966

I hope you know that not every equation have closed form solution.

--Nasser