Have you been taught synthetic division. I don't think there is an easier way to do this.
- 1 || 1 3 5 3
-1 -2 -3
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1 2 3 0
So the answer becomes
Length = x^2 + 2x +3 which isn't very nice to factor, but it is the length. Long division will give you exactly the same answer. And this cannot be reduced further and still give answers in the real realm of numbers.