a) (2x + y)(2x² - 2xy + 3)
= 2x.2x² -2x.2xy + 2x.3 + y.2x² - y.2xy + y.3
= 4x³ - 4x²y + 6x + 2x²y - 2xy² + 3y
= 4x³ - 2x²y - 2xy² + 6x + 2y
b) (x³ + 5x² + 5x - 3) : (x + 3)
= (x³ + 3x² + 2x² + 6x - x - 3) : (x + 3)
= [(x³ + 3x²) + (2x² + 6x) - (x + 3)] : (x + 3)
= [x²(x + 3) + 2x(x + 3) - (x + 3)] : (x + 3)
= (x + 3)(x² + 2x - 1) : (x + 3)
= x² + 2x - 1