Question 38829
<pre><font size = 5><b>To rationalize the denominator means to get rid of any
radicals in the denominator.

   _
  <font face = "symbol">Ö</font>3 - 2
————<u>—</u>—————
 -5<font face = "symbol">Ö</font>3 + 8

Since the denominator contains more than one term, at 
least one of which is a square root radical.


We create the "conjugate surd" of the denominator by 
changing only the sign of one of the (in this 'the only')
square root radical term. This expression we create is 
   _
+5<font face = "symbol">Ö</font>3 + 8

Then we place it over itself:

    _
  5<font face = "symbol">Ö</font>3 + 8
 ———<u>—</u>————
  5<font face = "symbol">Ö</font>3 + 8

which equals 1.  Therefore we can multiple the original
expression by this fraction which does not change its 
numerical value, because we can multiply any expression
by 1 without changing its numerical value.

   _           _
  <font face = "symbol">Ö</font>3 - 2     5<font face = "symbol">Ö</font>3 + 8
———<u>—</u>————— × ———<u>—</u>—————
 -5<font face = "symbol">Ö</font>3 + 8    5<font face = "symbol">Ö</font>3 + 8

Indicate the product of the numerators and denominators 
as one fraction:
   _           _
  <font face = "symbol">Ö</font>3 - 2     5<font face = "symbol">Ö</font>3 + 8
————<u>—</u>———— × ———<u>—</u>—————
 -5<font face = "symbol">Ö</font>3 + 8    5<font face = "symbol">Ö</font>3 + 8

   _        _
 (<font face = "symbol">Ö</font>3 - 2)(5<font face = "symbol">Ö</font>3 + 8)
————<u>—</u>————————<u>—</u>—————
(-5<font face = "symbol">Ö</font>3 + 8)(5<font face = "symbol">Ö</font>3 + 8)


Use FOIL to multiply out the numerator and denominator:

    _    _      _      _
  (<font face = "symbol">Ö</font>3)(5<font face = "symbol">Ö</font>3) + 8<font face = "symbol">Ö</font>3 - 10<font face = "symbol">Ö</font>3 - 16
————<u>—</u>————<u>—</u>————————<u>—</u>——————<u>—</u>————
(-5<font face = "symbol">Ö</font>3)(5<font face = "symbol">Ö</font>3)  - 40<font face = "symbol">Ö</font>3 + 40<font face = "symbol">Ö</font>3 + 64
           _
   5·3 - 2<font face = "symbol">Ö</font>3 - 16
 —————————————————
    -25·3 + 64
          _
   15 - 2<font face = "symbol">Ö</font>3 - 16
 —————————————————
    -75 + 64
         _
  -1 - 2<font face = "symbol">Ö</font>3 
 ——————————
    -11

to get rid of the negative signs multiply by the
fraction (-1)/(-1)
               _
 -1    (-1 - 2<font face = "symbol">Ö</font>3)   
———— × —————————— 
 -1        -11 
           _
 -1(-1 - 2<font face = "symbol">Ö</font>3)   
—————————————— 
   (-1)(-11)

        _
  1 + 2<font face = "symbol">Ö</font>3
 ————————— 
    11

Edwin
AnlytcPhil@aol.com</pre>