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C

chaugiang81

bài 1


$16^5 + 2^{15} $
$= 16^5 + (2^3)^5$
$= 16^5 + 8^5 $
$= 8^5(2^5 + 1) $
$= 8^5 . 33$ chia hết cho 33
 
I

iceghost

Bài 1
$16^5+2^{15} \\
= 2^{20}+2^{15} \\
= 2^{15}.(2^{5}+1) \\
= 2^{15}.(32+1) \\
= 2^{15}.33 \; \vdots \; 33$

Bài 2
$abcd = 100ab+cd \\
= 99ab + (ab+cd) \;\vdots \;99 \\
\implies ab+cd \;\vdots \; 99$

$\text{Ngược lại :} ab+cd \; \vdots \;99\\
\implies 99ab + (ab+cd) \;\vdots \;99 \\
= 100ab+cd = abcd \; \vdots \;99$
 
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