Đáp án:

 

Giải thích các bước giải:

3.$(5x+ \frac{2}{3} )^{2}$ = $\frac{4}{3}$

⇒ $(5x+ \frac{2}{3} )^{2}$= $\frac{4}{9}$

⇒ $25x^{2}$ + 2.5x.$\frac{2}{3}$ +$\frac{4}{9}$ = $\frac{4}{9}$

⇒ $25x^{2}$ +$\frac{20}{3}$ x=0

⇒ x.(25x+$\frac{20}{3}$ ) =0

⇒ $\left \{ {{x=0} \atop {25x+\frac{20}{3}=0}} \right.$

⇒ $\left \{ {{x=0} \atop {x=\frac{-4}{15}}} \right.$ 

Đáp án:

$\text{x = 0 hoặc x = -$\dfrac{4}{15}$.}$

Giải thích các bước giải:

`3(5x + 2/3)^2 = 4/3.`

`⇒(5x + 2/3)^2 = 4/3 ÷ 3.`

`⇒(5x + 2/3)^2 = 4/3 . 1/3.`

`⇒(5x + 2/3)^2 = 4/9.`

`⇒(5x + 2/3)^2 = (±2/3)^2.`

$\text{⇒ 5x + $\dfrac{2}{3}$ = $\dfrac{2}{3}$ hoặc 5x + $\dfrac{2}{3}$ = -$\dfrac{2}{3}$.}$

$\text{* Trường hợp 1: 5x + $\dfrac{2}{3}$ = $\dfrac{2}{3}$.}$

$\text{⇒ 5x = $\dfrac{2}{3}$ - $\dfrac{2}{3}$.}$

$\text{⇒ 5x = 0.}$

$\text{⇒ x = 0.}$

$\text{* Trường hợp 2: 5x + $\dfrac{2}{3}$ = -$\dfrac{2}{3}$.}$

$\text{⇒ 5x = -$\dfrac{2}{3}$ - $\dfrac{2}{3}$.}$

$\text{⇒ 5x = -$\dfrac{4}{3}$.}$

$\text{⇒ x = -$\dfrac{4}{3}$ ÷ 5.}$

$\text{⇒ x = -$\dfrac{4}{3}$.$\dfrac{1}{5}$.}$

$\text{⇒ x = -$\dfrac{4}{15}$.}$

$\text{Vậy x = 0 hoặc x = -$\dfrac{4}{15}$.}$