Simplify each expression. Use only positive exponents.
(2r^-1 s^2 t^0)^-2 /2rs 
Note: I left a space in the parenthesses so that you 
would know that 2r^-1, s^2 and t^0 are in the 
parenthesses.



Give every factor an exponent of 1 if none shows



We divide top and bottom by 



We know that  equals 1, so



We can dispense with the 1



Now we use the rule for getting rid of negative
exponents.  The rules are:

1. If a factor of the numerator has a negative
   exponent, then eliminate base and exponent
   from the numerator, and place a factor which
   has the same base but the opposite signed,
   i.e., positive exponent, as a factor of the
   denominator.

2. If a factor of the denominator has a negative
   exponent, then eliminate base and exponent
   from the denominator, and place a factor which
   has the same base but the opposite signed,
   i.e., positive exponent, as a factor of the 
   numerator. 

We need the first rule to eliminate the 
from the numerator and place  in the
denominator. 



Next we add the exponents of r in the denominator, i.e.
 =  = 




Finally subtract the exponents of s, 2-1 = 1,



or just



Edwin