Đáp án + Giải thích:
$\text{a) $6^{2x - 1}$ = 216.}$
$\text{⇒ $6^{2x - 1}$ = $6^3$.}$
$\text{⇒ 2.x - 1 = 3.}$
$\text{⇒ 2x = 3 + 1.}$
$\text{⇒ 2x = 4.}$
$\text{⇒ x = 2.}$
$\text{Vậy x = 2.}$
$\text{b) $3^{x + 1}$ + 7.$3^x$ = 270.}$
$\text{⇒ $3^{x}$.3 + 7.$3^x$ = 270.}$
$\text{⇒ $3^{x}$.(3 + 7) = 270.}$
$\text{⇒ $3^{x}$.10 = 270.}$
$\text{⇒ $3^{x}$ = 270 ÷ 10.}$
$\text{⇒ $3^{x}$ = 27.}$
$\text{⇒ $3^{x}$ = $3^3$.}$
$\text{⇒ x = 3.}$
$\text{Vậy x = 3.}$
