-4 | 1 9 23 8 -16
| -4 -20 -12 16
|_________________________________
1 5 3 -4 0
-4 | 1 5 3 -4
| -4 -4 4
|____________________________
1 1 -1 0
-4 | 1 1 -1
| -4 12
|_______________________
1 -3 11
-4 is a zero of the function shown at multiplicity 2.