Radicals cannot exist as a denominator, so you would multiply both Sqrt96 and Sqrt8 by the Sqrt8, giving you Sqrt768 over 8 (since a sqrt times itself is the base number, in this case 8) then you would simplify Sqrt768 into 16 x Sqrt3, leaving you with 16xSqrt3 over 8. simplify into 2Sqrt3 by dividing.
In general: <span>(a - b)^3 = a^3 - 3 a^2b + 3 a b^2 - b<span>^3
(4x-2y)^3 = </span></span>(4x)^3 - 3 (4x)^2(2y) + 3 (4x) (2y)^2 - (2y)^3
Since 3 divides 42, 3xy itself is the greatest common factor of 3xy and 42xy.
Answer: 3xy