If its asking you to expand use foil
rewrite as a double bracket
(3x+6)(3x+6)
multiply the first terms of each bracket
3x*3x=9x^2
multiply the outside terms on each bracket
3x*6=18x
multiply the inside terms on each bracket
6*3x=18x
multiply the last terms in each bracket
6*6=36
Collect the terms
9x^2+18x+18x+36
Simplify
9x^2+36x+36
