b) (x² – 2xy)(x³ + 3x²y – 5xy² – y³).

b) (x² – 2xy)(x³ + 3x²y – 5xy² – y³)

= x²(x³ + 3x²y – 5xy² – y³) ‒ 2xy(x³ + 3x²y – 5xy² – y³)

= x⁵ + 3x⁴y ‒ 5x³y² ‒ x²y³ ‒ 2x⁴y ‒ 6x³y² + 10x²y³ + 2xy⁴

= x⁵ + (3x⁴y ‒ 2x⁴y) + (‒5x³y² ‒ 6x³y²) + (‒x²y³ + 10x²y³) + 2xy⁴

= x⁵ + x⁴y ‒ 11x³y² + 9x²y³ + 2xy⁴.