@gimbell - Rationalizing numerators isn't so tough once you get a few formulas under your belt. It's also important to know if you need to take any higher math classes, like calculus.
Since I can't type in formulaic symbols here in the comment window, I'm going to do what my calculator's buttons do and type "sqrt()" for the square root of the number inside the parentheses. To show when something is squared, I'll put "^2".
Here we go.
To rationalize a numerator (or a denominator, actually) that contains an expression such as the following:
sqrt(a) - (sqrt(b)
...then you would multiply both the numerator and the denominator by what is called a conjugate radical -- the conjugate radical for the above expression looks like this:
sqrt(a) + (sqrt(b)
After you multiply the numerator and the denominator by the conjugal radical, you use the formula for finding the difference of a square on the results and you're done. Not too tough, right?
The formula for finding the difference of a square is as follows:
(sqrt(a) - sqrt(b)) (sqrt(a) + sqrt(b)) = sqrt(a)^2 - sqrt(b)^2 = a - b
Hope this helps!