Question

am nevoie urgent!!!dau coroană​

Answer 1

$a=3^{n+3}\cdot4^n+3^{n+1}\cdot4^{n+2}-3^{n+2}\cdot4^{n+1}=\\3^3\cdot (3\cdot4)^n+3\cdot4^2\cdot(3\cdot4)^n-3^2\cdot4\cdot(3\cdot4)^n=\\12^n(27+48-36)=39\cdot12^n \implies 39|a \ \forall n\in \mathbb{N}$