Question 609732
square root of -6 and -42. 
Both numbers are next to each other with the square root sign in front of each number.
:
{{{sqrt(-6) * sqrt(-42)}}} 
extract the square root of -1; i; multiply the values
{{{i*sqrt(6) * i*sqrt(42)}}} = {{{i^2*sqrt(6*42)}}} = {{{-1*sqrt(252)}}}
Factor to reveal a perfect square
{{{-1*sqrt(36*7)}}}
Extract the square root of 36
{{{-6*sqrt(7)}}}