Question 336119
{{{(sqrt(5)+3sqrt(8))(sqrt(5)-3sqrt(8))}}}
You could use FOIL to multiply this. But the easy way is to recognize that
{{{(sqrt(5)+3sqrt(8))(sqrt(5)-3sqrt(8))}}}
fits the pattern of
{{{(a+b)(a-b) = a^2 - b^2}}}
with
{{{a = sqrt(5)}}} and {{{b = 3sqrt(8)}}}.
So
{{{(sqrt(5)+3sqrt(8))(sqrt(5)-3sqrt(8)) = (sqrt(5))^2 - (3sqrt(8))^2 = 5 - 9*8 = 5 - 72 = -67}}}