Tính: b) (2x – 1)2 – 4(x – 2)(x + 2).
Tính:
b) (2x – 1)2 – 4(x – 2)(x + 2).
b) (2x – 1)2 – 4(x – 2)(x + 2)
= 4x2 – 4x + 1 – 4(x2 – 4)
= 4x2 – 4x + 1 – 4x2 + 16
= (4x2 – 4x2) – 4x + (1 + 16)
= – 4x + 17.