Nếu sao chép thì mod cho em xin cái link ạ .
`\text{@Jack}`
`2x - x^2 + \sqrt{(6x^2-12x+7)} = 0`
`⇔ 6x^2 - 12x + 7 = x^4 - 4x^3 + 4x^2`
`⇔ x^4 - 4x^3 + 4x^2 - 7 = 6x^2 - 12x`
`⇔ x^4 - 4x^3 - 2x^2 + 12x - 7 = 0`
Đặt `x^2 = t(t\ge0)`
`⇔ x^2-4t^2-2t+12x-7=0`
`⇔ x^2 - 2x - 7x = 0`
`⇔ x = 1\pm2\sqrt{2}`
Vậy `S = {1\pm2\sqrt{2}}`