Question 6415
i assume you mean... {{{(2sqrt(5))(3sqrt(5))- sqrt(45)}}}? If so, we get...


{{{2*3*sqrt(5)*sqrt(5) - sqrt(45)}}}
{{{6*sqrt(5)*sqrt(5) - sqrt(45)}}}
{{{6*5 - sqrt(45)}}} since {{{sqrt(5)*sqrt(5)}}} is 5
{{{30 - sqrt(45)}}}


ok, now for the {{{sqrt(45)}}}...


{{{30 - sqrt(9*5)}}}
{{{30 - sqrt(9)sqrt(5)}}}
{{{30 - 3sqrt(5)}}} --> this is an answer or we could factorise further to give:
{{{3(10 - sqrt(5))}}}


jon.