So sánh luỹ thừa?

H

harrypham

$3^{21}=3^{20} \times 3 = (3^2)^{10} \times 3 = 9^{10} \times 3$.
$2^{31}=2^{30} \times 2 = (2^3)^{10} \times 2 = 8^{10} \times 2$.
Ta có $9^{10} \times 3 > 8^{10} \times 2 \implies 3^{21}>2^{31}$.
 
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