Need to find x intercepts Using Matlab

Hi,

I have the following function and I am supposed to find the # of x intersects within the domain of [-20, 5].

3*x^2-1 = exp(-0.5*x)

I have the following commands typed into my script.

func = inline('3*x^2-1-exp(-0.5*x)')
fzero(func,[-20,5])

I am getting only 1 value showing me the x intercept but i am sure there are more than 1 intercepts.

How can i find all the x Intercepts.

PLEASE HELP...!!

[Soliver Fusi]

fsolve: fzero I think only works for one point

Answer 1

[Walter Roberson]

fzero() only calculates one intercept.

Plot the function and use the result to divide the distance between [-20, 5] into as many sub-ranges as necessary, each containing one intercept. Then fzero() over each of those sub-ranges.

[Ravi]

I actually figured this out and I have already done it that way using -20,-10 -10,0 0,5. I was wondering if there is one command which will give all three intercepts using one range.

Thank you very much for taking time to respond.

[Walter Roberson]

No, there is no command that can be given an arbitrary function and will return all of its zeros. There is a contribution from Roger Stafford in the File Exchange that tries to return multiple roots.

[Ravi]

Thank you very much.

[Walter Roberson]

Note: returning all zeros of an arbitrary function is a theoretical impossibility.