Tìm x, biết 4x(x + 1) + (3 – 2x)(3 + 2x) = 15

4x(x + 1) + (3 – 2x)(3 + 2x) = 15

⇔4x² + 4x + (9 – 4x²) = 15

⇔ 4x² + 4x + 9 – 4x² = 15

⇔4x = 15 – 9

⇔4x = 6

⇔x = 3/2