Factor $LaTeX: \displaystyle - 28 x^{3} - 36 x^{2} + 28 x + 36$ .

Factoring out the GCF $LaTeX: \displaystyle -4$ from each term gives $LaTeX: \displaystyle -4(7 x^{3} + 9 x^{2} - 7 x - 9)$ . Grouping the first two terms and factoring out their GCF, $LaTeX: \displaystyle x^{2}$ , gives $LaTeX: \displaystyle x^{2}(7 x + 9)$ . Grouping the last two terms and factoring out their GCF, $LaTeX: \displaystyle -1$ , gives $LaTeX: \displaystyle -1(7 x + 9)$ . The polynomial now has a common binomial factor of $LaTeX: \displaystyle 7 x + 9$ . This gives $LaTeX: \displaystyle -4[x^{2} \left(7 x + 9\right) -1 \cdot \left(7 x + 9\right)] = -4\left(7 x + 9\right) \left(x^{2} - 1\right)$ . The quadratic factor can be factored using the difference of squares to give $LaTeX: \displaystyle -4\left(x - 1\right) \left(x + 1\right) \left(7 x + 9\right).$