Question

VA ROG REPEDE AM TEST (PATRATELE SUNT SEMNE DE INMULTIRE) ​

Answer 1

$\displaystyle\bf\\A=3^{n+1}\cdot4^{n+2}-3^{n+2}\cdot4^{n+1}+3^{n+3}\cdot4^n =\\3^n\cdot4^n\cdot3\cdot4^2-3^n\cdot4^n\cdot3^2\cdot4 + 3^n\cdot4^n\cdot3^3=\\3^n\cdot4^n(3\cdot16-9\cdot4+27)=3^n\cdot4^n\cdot 39=3^n\cdot4^n\cdot3\cdot13~\vdots~13,~evident.$