Answer
54$a^{2}$+36a+6
Work Step by Step
Let a be the lenth of a side of a cube
Formula of surface area of a cube: 6$a^{2}$
Plug in value for a: 6$(3a+1)^{2}$
=6(3a+1)(3a+1)
=6(9$a^{2}$+3a+3a+1) (FOIL-First Inside Outside Last)
=6(9$a^{2}$+6a+1) (Combine like terms)
=54$a^{2}$+36a+6
