`2.`
`a):`
`2`$\sqrt[]{x}$ `- 1 = 3`
`⇔ 2`$\sqrt[]{x}$ `- 1−(−1)=3−(−1)`
`⇔ 2`$\sqrt[]{x}$ `=3−(−1)`
`⇔ 2`$\sqrt[]{x}$ `= 4`
`⇔` $\dfrac{2\sqrt[]{x}}{2}$ `= 4/2`
`⇒` $\sqrt[]{x}$ `= 4/2`
`⇒` $\sqrt[]{x}$ `= 2`
`⇒ x = 2 × 2`
`x = 4`
Cho mình xin hay nhất nha bạn
@Drew Mclntyre