Eg if you compare (x + 1.2) + (x + 2.3) < (2*x + 3.6) that goes wrong for big enough x.
You know that at big enough values, floating point numbers are farther apart than integers?
Eg if you compare (x + 1.2) + (x + 2.3) < (2*x + 3.6) that goes wrong for big enough x.