Đáp án:
$\text{a) x = 2}$
$\text{b) x = 4}$
Giải thích các bước giải:
$\text{(a (2x + 1)³ = 125}$
$\text{⇔ (2x + 1)³ = 5³}$
$\text{⇔ 2x + 1 = 5}$
$\text{⇔ 2x = 5 - 1}$
$\text{⇔ 2x = 4}$
$\text{⇔ x = 4 : 2}$
$\text{⇒ x = 2}$
$\text{Vậy: x = 2}$
$\text{b) (4x - 1)² = 25 . 9}$
$\text{(4x - 1)² = 3² . 5²}$
$\text{4x - 1 = 3 . 5}$
$\text{4x - 1 = 15}$
$\text{4x = 15 + 1}$
$\text{4x = 16}$
$\text{x = 16 : 4}$
$\text{x = 4}$
$\text{Vậy: x = 4}$
