To simplify this expression, we will apply a method called FOIL.
FOIL stands for First, Outer, Inner, Last.
If we multiply the first terms, we get a^2.
If we multiply the outer terms, we'll get 3ab.
If we multiply the inner terms, we'll get 2ab.
If we multiply the last terms, we'll get 6b².
The result is a² + 3ab + 2ab + 6b².
Answer: