Answer
$$3(m+\sqrt 3)(m-\sqrt 3)$$
Work Step by Step
Factor
$$3m^{2}-9.$$
First factor out a $3$:
$$3(m^{2}-3)$$
Find two numbers that are factors of $-3$ and sum to $0$:
$$(\sqrt 3)(-\sqrt 3)=-3;\space \sqrt 3-\sqrt 3=0.$$
The polynomial is a product of two binomials:
$$3(m^{2}-3)=3(m+\sqrt 3)(m-\sqrt 3).$$
