Question

Afla ultima cifra a nr 2+2^2+ 2^3+. +2^56.

Answer 1

Răspuns:

0

Explicație pas cu pas:

$2 + {2}^{2} + {2}^{3} + ... + {2}^{56} = \dfrac{2 \cdot ({2}^{56} - 1)}{2 - 1} = {2}^{57} - 2$

$u({2}^{57} - 2) = u(u({2}^{57}) - u(2)) = u(u({2}^{56 + 1}) - 2) \\ = u(u(({2}^{4})^{14} \cdot 2) - 2) = u(u(2) - 2) = u(2 - 2) =$

$= u(0) = 0$