how to set the domain of a function

Hello please how do I set the domain for my function :

 f(x1,x2)= -9*x(1) - 10*x(2) + 10*(-log(100-x(1)-x(2))-log(x(1))-log(x(2))-log(50-x(1)+x(2))); 
X{(x1,x2)|x1>0,x2>0,x1+x2<100,x1-x2<50}

thanks

Answer 1

[Walter Roberson]

syms x [1 2]
f(x) = piecewise(x(1)>0 & x(2)>0 & x(1)+x(2) <100 & x(1)-x(2)<50, -9*x(1) - 10*x(2) + 10*(-log(100-x(1)-x(2))-log(x(1))-log(x(2))-log(50-x(1)+x(2))), NaN)

f(x1, x2) = 

fsurf(f, [-5 105 -5 105] ); xlim([-5 105]); ylim([-5 105])

[Patience Shamaki]

Thank you very much it worked!

[Patience Shamaki]

Just one more doubt, so that I can understand what I did better

syms x[1 2] keeps giving me this error:

Error using syms (line 293)

Invalid variable name.

Error in text_line (line 3)

syms x[1 2];

so I did: syms x1 x2;

x=[1 2]

and it worked, just wondering if it makes any difference expecially since because of the function:

f(x1,x2)=....

[Walter Roberson]

syms x [1 2]

Notice the space.

However I see now that you are using an older release. You would need

x = sym('x', [1 2]);

[Patience Shamaki]

Okay, thank you very much!!