Hint:
A= [2 3 5];
disp([num2str(A(1)),'.*X + ',num2str(A(2)),'.*Y + ',num2str(A(3))])
2.*X + 3.*Y + 5
The above is only a complete guess as to what you intend. Note that it can be pretty easily extended to a general case, where you write a small helper function that takes a list of terms and coefficients, then creates a string. With just a wee bit of effort, you can make it handle a general nonlinear case. But you need to decide how generally nonlinear a function you may have.
The point is, write a simple function that will take some functional form, with a coefficient or coefficients, returning a string. Then just loop over the terms, and build up a complete string of terms. (Not difficult, since I recall doing exactly this many years ago.)
As I said, only a guess though.
