`a):`
$\sqrt[]{x_2}$ `= 6`
`⇒ x_2 = 36`
`b):`
$\sqrt[]{9x_2}$ `= |12|`
`⇔ 9x_2 = 144`
`⇔ (9x_2)/9 = 144/9`
`⇒ x_2 = 144/9`
`⇒ x_2 = 16`
`c):`
`2`$\sqrt[]{x2}$ `= 8`
`⇔` $\dfrac{2\sqrt[]{x_2} }{2}$ `= 8/2`
`⇔` $\sqrt[]{x_2}$ `= 8/2`
`⇒` $\sqrt[]{x_2}$ `= 4`
`⇒ x_2 = 16`
Cho mình xin hay nhất nha bạn
@Drew Mclntyre