Question 34713
{{{ sqrt(6) (sqrt(6) - sqrt(10)) }}}
Alright, first thing, lets make this a simpler problem
{{{ x (x - y) }}}
When solving this we distribute 
{{{ x^2 - xy }}}
Using this formula, lets distribute the first expression
{{{ sqrt(6) (sqrt(6) - sqrt(10)) }}}
{{{ (sqrt(6))^2 - (sqrt(6))(sqrt(10)) }}}
When you have a root and a square, they cancel one another and leave the number that is in the root.  So, therefore, the first number is just 6
{{{ 6 - (sqrt(6))(sqrt(10)) }}}
When multiplying roots, they can move under one root.
{{{ 6 - (sqrt(6*10)) }}}
Factor the root
{{{ 6 - (sqrt(2*3*2*5)) }}}
Take the pairs that are under the root, to the outside, but when you do this, one of the pair disappears.
{{{ 6 - 2(sqrt(3*5)) }}}
Multiply what is left under the root
{{{ 6 - 2(sqrt(15)) }}}
DONE