Add helpful example

Author: adiaholic

Doc/library/functions.rst

@@ -1561,7 +1561,9 @@ are always available.  They are listed here in alphabetical order.
    returns ``100``, but ``pow(10, -2)`` returns ``0.01``.  For a negative base of
    type :class:`int` or :class:`float` and a non-integer exponent, a complex
    result is delivered.  For example, ``pow(-9, 0.5)`` returns a value close
-   to ``3j``.
+   to ``3j``. Whereas, for a negative base of type :class:`int` or :class:`float`
+   with an integral exponent, a real number is delivered. For example, 
+   ``pow(-9, 2.0)`` returns ``81.0``.
 
    For :class:`int` operands *base* and *exp*, if *mod* is present, *mod* must
    also be of integer type and *mod* must be nonzero. If *mod* is present and