SOLUTION: {{{sqrt(5^99x^87y^64)}}}

The index of a square root is 2, so we write:



Divide the index into each exponent.

Divide index 2 into the first exponent 99
  
  49
2)99
  98
   1 

49 is the quotient, so we will have  on
the outside in front of the radical.

1 is the remainder, so we will have  left
under the radical.  So far we have this:



 ---

Divide index 2 into the second exponent 87
  
  43
2)87
  86
   1 

43 is the quotient, so we will have  on
the outside in front of the radical.

1 is the remainder, so we will have  left
under the radical.  So far we have this:



 ---

Divide index 2 into the third exponent 64
  
  32
2)64
  64
   0 

32 is the quotient, so we will have  on
the outside in front of the radical.

0 is the remainder, so we will have no y's left
under the radical.  So we have:



But of course when the root is a square root,
we do not write the index, so we will drop the
index 2, and the 1 exponents as well:



Edwin