Factor $LaTeX: \displaystyle - 20 x^{3} - 16 x^{2} + 90 x + 72$ .

Factoring out the GCF $LaTeX: \displaystyle -2$ from each term gives $LaTeX: \displaystyle -2(10 x^{3} + 8 x^{2} - 45 x - 36)$ . Grouping the first two terms and factoring out their GCF, $LaTeX: \displaystyle 2 x^{2}$ , gives $LaTeX: \displaystyle 2 x^{2}(5 x + 4)$ . Grouping the last two terms and factoring out their GCF, $LaTeX: \displaystyle -9$ , gives $LaTeX: \displaystyle -9(5 x + 4)$ . The polynomial now has a common binomial factor of $LaTeX: \displaystyle 5 x + 4$ . This gives $LaTeX: \displaystyle -2[2 x^{2} \left(5 x + 4\right) -9 \cdot \left(5 x + 4\right)] = -2\left(5 x + 4\right) \left(2 x^{2} - 9\right)$ .