The critical values are

x = -3, x = 2 and x = 4.

These critical values divide the number line into 4 intervals.

Hence, the signs of the function are:

Interval		sign of f(x)
x < -3		-
-3 < x < 2		+
2 < x < 4		+
x > 4		-

Since we want f(x) < 0, the intervals that satisfy this inequality will be those with a negative sign.

Hence, the solution is: x < -3 or x > 4.