[tex](3^n+5*3^{n+1}+8*3^{n+2} -3^{n+3} ) : 61 \\\\ (In \ loc \ de \ : \ trebuie \ sa \ pui \ 3 \ puncte) \\\\\\ (3^n+5*3^n*3+8*3^n*3^2-3^n*3^3):61 \\\\ (3^n+15*3^n+8*9*3^n-3^n*27):61 \\\\ 3^n(1+15+72-27):61 \\\\ 3^n(88-27):61 \\\\ \boxed{3^n*61 :61}[/tex]
