x^2 -12*x-96 = 0 giải pt áa

`x^2 - 12.x - 96 = 0`

`⇔ x^2 - 2.6.x + 6^2 - 6^2 - 96 = 0`

`⇔ ( x^2 - 2.6.x + 6^2 ) - 36 - 96 = 0`

`⇔ ( x - 6 )^2 - 132 = 0`

`⇔ ( x - 6 )^2          = 132`

`⇔ x - 6                   = ±sqrt{132}`

`TH1 : `

`x - 6 = sqrt{132}`

`x       = sqrt{132} + 6`

`TH2 : `

`x - 6 = -sqrt{132}`

`x       = -sqrt{132} + 6`

`x       = 6 - sqrt{132}`

Vậy `S = { sqrt{132} + 6 ; 6 - sqrt{132} }`