Tính:

a) (x³ + 3x² – 5x – 1)(4x – 3);

b) \(\left( { - 2{x^2} + 4x + 6} \right)\left( { - \frac{1}{2}x + 1} \right)\).

a) (x³ + 3x² – 5x – 1)(4x – 3);

= 4x⁴ – 3x³ + 12x³ – 9x² – 20x² + 15x – 4x + 3

= 4x⁴ + (−3x³ + 12x³) + (−9x² – 20x²) + (15x – 4x) + 3

= 4x⁴ + 9x³ – 29x² + 11x + 3.

b) \(\left( { - 2{x^2} + 4x + 6} \right)\left( { - \frac{1}{2}x + 1} \right)\).

= x³ – 2x² – 2x² + 4x – 3x + 6