khó

C

chaugiang81

$\dfrac{1}{4}.\dfrac{2}{4}.\dfrac{3}{8}.\dfrac{4}{10}.....\dfrac{30}{62}.\dfrac{31}{64}=2^n$
$<=> \dfrac{1.2.3.4....31}{4.6.8.10.......62.64}=2^n$
$<=>\dfrac{1.2.3.4....31}{2(2.3.4.5.6.....32)}=2^n$
$<=> \dfrac{1}{64} = 2^n$
$=>1= 2^n . 64 $
$=>1= 2^n . 2^6 $
$=>1= 2^{n+6}$
$<=> n+6= 0 vì 2^0 = 1$
$=>n=-6$
 
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