Tìm x, biết: 4x^2 – 25 – (2x – 5)(2x + 7) = 0
Tìm x, biết: 4x2 – 25 – (2x – 5)(2x + 7) = 0.
4x2 – 25 – (2x – 5)(2x + 7) = 0
⇔ (4x2 – 25) – (2x – 5)(2x + 7) = 0
⇔ (2x – 5)(2x + 5) – (2x – 5)(2x + 7) = 0
⇔ (2x – 5)(2x + 5 – 2x – 7) = 0
⇔ (2x – 5).(–2) = 0
⇔ 2x – 5 = 0
⇔ \(x = \frac{5}{2}\)
Vậy \(x = \frac{5}{2}\).