To find the other factors we start by dividing by the known factor, x+5. I prefer synthetic division over long division:
-5 | 1 2 -33 -90
--- -5 15 90
--------------------
1 -3 -18 0
The remainder, in the lower right corner, is zero. This is to be expected when x+5 was supposed to be a factor. The other factor is found in the front of the remainder: 1 -3 -18. This translates into . Now we just factor that:
So your expression, fully factored, is: