Phân tích đa thức thành nhân tử: 4x^2 – 25 + (2x + 7)(5 – 2x).
Ta có:
4x2 – 25 + (2x + 7)(5 – 2x)
= (2x)2 – 52 + (2x + 7)(5 – 2x)
= (2x – 5)(2x + 5) – (2x + 7)(2x – 5)
= (2x – 5)(2x + 5 – 2x – 7)
= –2(2x – 5).