Differentiate without symbolic toolbox

I am trying to evaluate this:

d2(Px^(2/3))/dx2

d(Px^(2/3)/dx

P is an array (1,100);

I calculated x for each P.

I want to get these for each value of P.

Thank you for your help. I do not have the sym toolbox.

[Rik]

Since P is a constant in x, can't you just manually derive the function and then multiply?

I must also admit I don't really understand what you have and what you want.