Question 165005
{{{9*sqrt(18) - 6*sqrt(2)}}}
Factor numbers inside radical to it's prime numbers:
{{{9*sqrt(2*3*3) - 6*sqrt(2)}}}
Pull out "pairs" of like numbers:
{{{9*3*sqrt(2) - 6*sqrt(2)}}}
{{{27*sqrt(2) - 6*sqrt(2)}}}
Factor out sqrt(2):
{{{sqrt(2)(27 - 6)}}}
{{{sqrt(2)(21)}}}
{{{21*sqrt(2)}}}