Question 1119038
...  How do you know? 
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What does synthetic division give you?  Remainder or not?  If it gives a remainder, then this is the value of the function at x=-3.




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<pre>
-3   |    -3    6    6    9
     |          9  -45  117
     |_________________________
          -3   15  -39   126
</pre>
The remainder is 126, and this is not 0.