Question

Aratati ca numarul a=2^n + 2^n+1 + 2^n+2 se divide cu 7

Answer 1

Răspuns:

$a = 2 {}^{n} + 2 {}^{n + 1} + 2 {}^{n + 2}$

$a = 2 {}^{n} (1 + 2 {}^{1} + 2 {}^{2} )$

$a = 2 {}^{n} \times 7$

=>a se divide cu 7