This one's kinda tricky
Start by putting parenthesis around the first two terms and last two terms
(x^3 - 3x^2) + (2x - 6)
Now, see what you can pull out.
In the first set, you can see they have an x^2 in common.
In the second set, they have a factor of 2 in common.
Therefore,
x^2(x - 3) + 2(x - 3)
combine the like terms to get
(x^2 + 2)(x - 3)