Đáp án + Giải thích các bước giải:
$\text{$3^{x}$ + $3^{3 + 2}$ = 270}$
$\text{⇔ $3^{x}$ + 243 = 270}$
$\text{⇔ $3^{x}$ = 27 = $3^{3}$ }$
$\text{ ⇒ x = 3}$
$\text{$5^{x}$ + $5^{x + 1}$ = 750 }$
$\text{$5^{x}$( 1 + 5) = 750}$
$\text{⇒ $5^{x}$ = 125 = $5^{3}$ }$
$\text{⇒ x =3}$
$\text{$2^{x + 3}$ + $2^{x}$ = 144}$
$\text{$2^{x}$ (8 + 1) = 144}$
$\text{⇔ $2^{x}$ = 16 = $2^{4}$ }$
$\text{⇔ x = 4}$
$\text{$7^{x}$ + $7^{ x+ 1}$ = 392}$
$\text{$7^{x}$ (1 + 7) = 392}$
$\text{⇔ $7^{x}$ = 49 = $7^{2}$ }$
$\text{⇒ x = 2}$
