"klutch " <klutch52@gmail.com> wrote in message <idb6u9$cej$1@fred.mathworks.com>...
> > Your use of DIFF and your use of the term "initial values" makes me think
> > you're trying to solve a differential equation (for which DSOLVE would be
> > the appropriate tool) but your xi doesn't include any derivative terms, so
> > I'm not _really_ sure what you're trying to do. Please reply and clarify
> > your exact goal.
>
> i have a function
>
> z = 6/5  ( 5*x^3 + 3*x^2 + (19*x)/4 + 3/4)/( 10*x^2 + x + 5*y + 1)
>
> now i want to know value of the z(x,y) function where x=1.2 and y=1.2.
>
> z(1.2 , 1.2) = ?
>
> but the function is symbolic, it's not double. how to solve symbolic function in certain value of x, y.
>
> 
> if the func is double, just write like that.
>
> x=1.2;
> y=1.2;
> z = 6/5  ( 5*x^3 + 3*x^2 + (19*x)/4 + 3/4)/( 10*x^2 + x + 5*y + 1)
>
> ans=1.5435
%%%%
syms x y
z = 6/5  ( 5*x^3 + 3*x^2 + (19*x)/4 + 3/4)/( 10*x^2 + x + 5*y + 1);
subs(z,{x y},{1.2 1.2})
