A factor by grouping approach works for the numerator.
6 x^3 + 24 x^2 - 2 x – 8
6 x^2 ( x +4 ) - 2 ( x +4) see that (x +4) appears in both groups so
(x + 4 ) ( 6 x^2 -2)
Since the denominator is x + 4, it cancels the x + 4 in the numerator leaving
6 x^2 -2 which factors as 2 ( sqrt(3) x -1 )( sqrt(3) +1)