If ( x + 3) is a factor of , then (x+3) will divide into evenly. And synthetic division is probably the easiest way to find out if (x+3) divides evenly:
-3 | 1 0 -2k k^2
---- -3 9 -27+6k
-----------------------
1 -3 9-2k k^2+6k-27
When a division works out evenly, the remainder is zero. So the value(s) of k that makes zero will be our answer(s):
This is a quadratic equation which we can solve by factoring or with the quadratic formula. It factors pretty easily:
By the Zero Product Property one of these factor must be zero:
or
Solving these we get:
or
So we have two possible values for k.