Final answer:
x1 and x1 represent the same variable and have the same meaning in mathematics.
Step-by-step explanation:
The difference between x1 and x1 does not exist because they are the same variable. They both represent the same value or object. In mathematics, when a variable is used, it typically represents an unknown or changing value. However, in this case, x1 and x1 are both the same variable and therefore have the same meaning.