Răspuns:
A=3^(2n+4)•7^(n+1)-(3^2 • 7)^(n+1)-3^(2n+3)•7^(n+1)
A=3^(2n+4)•7^(n+1)-3^(2n+2)•7^(n+1)-3^(2n+3)•7^(n+1)
A=3^(2n+2)•7^(n+1)•(3^2 - 1 - 3)
A=3^(2n+2)•7^(n+1)•5 sau
A=3^(2n+2)•7^n•7•5 sau
A=3^(2n+2)•7^n•35 divizibil cu 35
