Answer
$54a^{2}$+36a+6
Work Step by Step
1. surface area can be found using formula: A=$6s^{2}$
2. We have the side length of the cube: s=(3a+1)
3.Apply foil to A=$6s^{2}$
A=6[(3a+1)(3a+1)]
A=6[(3a)(3a)+(1)(3a)+(3a)(1)+(1)(1)]
A=6[$9a^{2}$+3a+3a+1]
A=6[$9a^{2}$+6a+1]
4. Simplify
A=$54a^{2}$+36a+6
