Question

Va rog djndbdbxbdbdbdbd

Answer 1

Răspuns:

Explicație pas cu pas:

a)

$a=1+3+3^{2} +3^{3} +...+3^{64} +3^{65} =4+3^{2} (1+3)+...+3^{64} (1+3)=\\ =4+4\cdot3^{2} +...+4\cdot3^{64} =4\cdot(1+3^{2} +...+3^{64} )$

a | 2 ⇒ a număr par

b)

$a=1+3+3^{2} +3^{3} (1+3+3^{2} )+...+3^{63} (1+3+3^{2} )= \\ =13+3^{3}\cdot13} +...+3^{63}\cdot13=\\ =13\cdot(1+3^{3} +...+3^{63} )$

⇒ a | 13