Find the anti-derivative of $LaTeX: \displaystyle f(x) = - x^{4} + 9 x^{3} - 5 x^{2} - 6 x + 6$ .

Using the power rule on each term gives $LaTeX: \displaystyle F(x) = - \frac{x^{5}}{5} + \frac{9 x^{4}}{4} - \frac{5 x^{3}}{3} - 3 x^{2} + 6 x + C$