Answer
$$=x^3+x^2-22x-40$$
Work Step by Step
In order to solve this problem, we follow order of operations. Thus, we multiply and apply exponents first, and then we add and subtract. Doing this, we find:
$$\left(x+2\right)\left(x+4\right)\left(x-5\right) \\ \left(x^2+6x+8\right)\left(x-5\right)\\=x^3+x^2-22x-40$$
