The value of the expression (x - 2)/(x + 2) depends upon the value of the variable x.
(x - 2)/(x + 2) equals -1 only when x is zero.
If x represents any number other than 0, then (x - 2)/(x + 2) does not equal -1.
If x represents the number -2, then the expression (x - 2)/(x + 2) does not equal anything; it's "undefined".