Tìm x biết: (2x + 3)^2 - (x - 4)(x + 4) - 3(x^2 + 3) = 0

Ta có: 2x+32−x−4x+4−3x2+3=0

                   ⇔2x+32−x−4x+4−3x2+3=0

                   ⇔4x2+12x+9−x2−16−3x2−9=0

                   ⇔4x2+12x+9−x2+16−3x2−9=0

                   ⇔12x+16=0⇔x=−1612=−43

Vậy x=−43