Answer
$$\left(x+6\right)\left(x+9\right)$$
Work Step by Step
In order to multiply factors out, we would use the FOIL method. This means that we multiply the first terms in each factor by each other. Then, we multiply the two outer terms by each other. Next, we multiply the two inner terms. Finally, we multiply the two terms that have yet to be multiplied by each other. Thus, we try to do the opposite of this to factor the equation.
$$x\left(x+6\right)+9\left(x+6\right) \\ \left(x+6\right)\left(x+9\right)$$
