Tìm x biết: (2x + 3)^2 - 4x(x + 4) = 25
Tìm x biết: (2x + 3)2 – 4x(x + 4) = 25.
(2x + 3)2 – 4x(x + 4) = 25
⇔ 4x2 + 12x + 9 – 4x2 – 16x – 25 = 0
⇔ –4x = 16
⇔ x = –4
Vậy x = –4.