To divide the polynomial \(x^4 + 3x^3 - x^2 - x + 6\) by \(x + 3\), we can use polynomial long division.
Divide the leading term of the numerator \(x^4\) by the leading term of the denominator \(x\) to get \(x^3\).
Multiply \(x^3\) by \(x + 3\) to get \(x^4 + 3x^3\).
Subtract \(x^4 + 3x^3\) from the original polynomial:
\[ (x^4 + 3x^3 - x^2 - x + 6) - (x^4 + 3x^3) = -x^2 - x + 6 \]
Now, take the next term in the result, \(-x^2\), and divide it by \(x\) to get \(-x\).
Multiply \(-x\) by \(x + 3\) to get \(-x^2 - 3x\).
Subtract this result from \(-x^2 - x + 6\):
\[ (-x^2 - x + 6) - (-x^2 - 3x) = 2x + 6 \]
Now divide \(2x\) by \(x\) which gives \(2\).
Multiply \(2\) by \(x + 3\) to get \(2x + 6\).
Subtract this from \(2x + 6\):
\[ (2x + 6) - (2x + 6) = 0 \]
So the division is complete, and we find that:
\[ \frac{x^4 + 3x^3 - x^2 - x + 6}{x + 3} = x^3 - x + 2 \]
Thus, the result of the division is:
\[ \boxed{x^3 - x + 2} \]