`x^2 - 3x - 1 = 0`

`x^2 - 3x + 9/4 - 13/4 =0`

`(x - 3/2)^2 = 13/4`

`(x - 3/2)^2 = (±\sqrt{13/4})^2`

`(x - 3/2)^2 = (±(\sqrt{13})/2)^2`
`x - 3/2 = ±(\sqrt{13})/2`
`TH1:`

`x - 3/2 = (\sqrt{13})/2`

`x = (\sqrt{13}+3)/2`
`TH2:`

`x - 3/2 = -(\sqrt{13})/2`

`x=(-\sqrt{13}+3)/2`

Vậy `x= (\sqrt{13}+3)/2` và `x = (-\sqrt{13}+3)/2`

$#rowena0123$