First of all the negative sign is not the sign of 27, for it is
the sign of the entire expression. The above is equivalent to
The exponent is negative which means that it is the reciprocal
of the expression with an exponent with the positive sign.
Now a fractional power with a 1 numerator is the root of the
base with the same index. So let's first write the fractional exponent 2/3
as (1/3)(2)
Then we use the law of multiplied exponents as
Go back to the rule that a fractional power with a 1 numerator is the
root of the base with the same index as the denominator of the
fractional exponent.
The cube root of 27 is 3, so we have
And since 3 squared is 9, we have
Edwin