Phân tích đa thức sau thành nhân tử

a) x² – 5x – 14;

b) 4x² – 3x – 1;

c) x⁴ + 64.

a) x² – 5x – 14

= x² – 7x + 2x – 14

= x(x – 7) + 2(x – 7)

= (x – 7)(x + 2)

b) 4x² – 3x – 1

= 4x² – 3x – 4 + 3

= 4(x² – 1) – 3(x – 1)

= 4(x – 1)(x + 1) – 3(x – 1)

= (x – 1)(4x + 4 – 3)

= (x – 1)(4x + 1)

c) x⁴ + 64

= x⁴ + 16x² + 64 – 16x²

= (x² + 8)² – 16x²

= (x² + 8 – 4x)(x² + 8 + 4x).