Originally Posted by
pickslides Here's one I prepared earlier.
Consider
$\displaystyle \frac{1}{4\sqrt{5}} $
Let's times it by 1 because that won't change anything
$\displaystyle \frac{1}{4\sqrt{5}}\times 1 $
But 1 comes in many forms I.e $\displaystyle \frac{a}{a}=1, a\neq 0 $
So lets make it the following
$\displaystyle \frac{1}{4\sqrt{5}}\times \frac{\sqrt{5}}{\sqrt{5}} $
I did this because $\displaystyle \sqrt{a}\times \sqrt{a}= a$
Now we have
$\displaystyle \frac{1\times \sqrt{5}}{4\sqrt{5}\times \sqrt{5}} $
$\displaystyle \frac{\sqrt{5}}{4\times 5} $
We have no radical in the denominator so we are finished.
Apply this method to your problem.