[Toán 9] Chia hết

I

icy_tears

Ta có:
$8351 \equiv 5$ (mod 26)
\Rightarrow $8351^{634} \equiv 5^{634} $ (mod 26)

$8241 \equiv 25$ (mod 26)
\Rightarrow $8241 \equiv -1$ (mod 26)
\Rightarrow $8241^{142} \equiv (-1)^{142}$ (mod 26)

\Rightarrow $8351^{634} + 8241^{142}$
$\equiv 5^{634} + (-1)^{142}$ (mod 26)
$\equiv 25^{317} + 1$ (mod 26)
$\equiv (-1)^{317} + 1$ (mod 26)
$\equiv -1 + 1$ (mod 26)
$= 0$
Vậy $8351^{634} + 8241^{142} \vdots \ 26$
 
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