Tìm x biết: (x + 2)(3x - 1) + 9x^2 1 = 0

(x + 2)(3x – 1) + 9x2 – 1 = 0

⇔ (x + 2)(3x – 1) + (3x – 1)(3x + 1) = 0

⇔ (3x – 1)(x + 2 + 3x + 1) = 0

⇔ (3x – 1)(4x + 3) = 0

⇔ 

⇔ 

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