\(\displaystyle \L 3x^3 - 24\)
Start by factoring out a 3
\(\displaystyle \L 3(x^3 - 8)\)
now use the difference of cubes theorm to factor into a binomial and a trinomial:
\(\displaystyle \L a^3-b^3 = (a-b)(a^2+ab+b^2)\)
now what to the third power, equals 8? 2^3 = 8, so we can write this as
\(\displaystyle \L 3(x^3 -2^3)\)
now use the difference of cubes, as I showed, above, and factor:
You end up with:
\(\displaystyle \L 3(x-2)(x^2+2x+4)\)
And that's your answer!
See how I did it? In this case, a = x and b = 2