Bài 5 :
a, A = $2^{300}$ và B = $3^{200}$
$2^{300}$ = ( $2^{3}$ )$^{100}$ = $8^{100}$
$3^{200}$ = ( $3^{2}$ )$^{100}$ = $9^{100}$
Vì $8^{100}$ < $9^{100}$
⇒ $2^{300}$ < $3^{200}$
b, A = $2020^{100}$ - $2020^{99}$ và B = $2020^{99}$ - $2020^{98}$
Ta có : $2020^{100}$ - $2020^{99}$ = $2020^{99}$ . ( 2020 - 1 ) = $2020^{99}$ . 2019
$2020^{99}$ - $2020^{98}$ = $2020^{98}$ . ( 2020 - 1 ) = $2020^{98}$ . 2019
Vì $2020^{99}$ . 2019 > $2020^{98}$ . 2019
⇒ $2020^{100}$ - $2020^{99}$ > $2020^{99}$ - $2020^{98}$
