Question 194357
1)
{{{(3sqrt(2))(-4sqrt(10))}}}
={{{3*(-4)sqrt(2)*sqrt(10)}}}
={{{-12sqrt(2*10)}}}
={{{-12sqrt(2^2*5)}}}
={{{-12*2*sqrt(5)}}}
={{{-24sqrt(5)}}}

2)
Use the formula {{{(a+b)(a-b)=a^2-b^2}}} to simplify
{{{(3-2sqrt(7))(3 +2sqrt(7))}}}
={{{3^2-(2sqrt(7))^2}}}
={{{9-2^2*(sqrt(7))^2}}}
={{{9-4*7}}}
={{{9-28}}}
={{{-19}}}