## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$2\sqrt 3$
To simplify the expression, we distribute (FOIL) and combine the like terms as follows: $$(\sqrt 3+3)(\sqrt 3-1)=(\sqrt 3)^2-\sqrt 3+3\sqrt 3-3\\ =3+2\sqrt 3-3=2\sqrt 3 .$$