Polynomials in different variables addition.

I wanted to add two or more polynomials with which are functions of different variables like 2x^2+3x+5 and 5y^2+8y+6 in matlab. i just need the answer for optimization purposes. i am aware that the constant part will only add up , but that's all i need. any help would be very much appreciated

[KSSV]

Is using symbolic calculation allowed?

syms x y
f1 = 2*x^2+3*x+5 ;
f2 = 5*y^2+8*y+6 ;
f = f1+f2

[Guillaume]

And if symbolic is not allowed, then it's not clear what's even being asked.

The sum of two independent functions of independent variables, f(x) and g(y) is ... drumroll ... f(x)+g(y). That f and g are polynomial functions does not matter. There's nothing to simplify.