How do I express the error values from math formula with matlab code

The formula is (x1-x2)/(10-2*x1)

And I want to say x1 is not able to equal to 5 in matlab code, how do I express this in codes?

[KALYAN ACHARJYA]

x1=input('Enter x1: ');
x2=input('Enter x2: ');
if x1==5
    disp('Invalid x1 value');
else
    fun=(x1-x2)/(10-2*x1);
    fprintf('The Function value is: %f',fun);
end