How to write this?

f(x)=(x1-1)^2+(x2-1)^2

Answer 1

[Rik]

To answer your question:

f(x)=(x1-1)^2+(x2-1)^2

To answer the question you meant to ask:

f=@(x1,x2) (x1-1).^2+(x2-1).^2;

Depending on what you want to do that might be the correct form.

If not, I suggest you do a basic Matlab tutorial (like e.g. Onramp) or take a look here for advice on how to improve your question.