The polynomial function has the form :

A = 3x²(x-1) = 3x³ - 3x²
B = -3x³ + 4x² -2x + 1
A + B = (3x³ - 3x²) + (-3x³ + 4x² -2x + 1) = x² - 2x + 1
∴ Yes, The result of (A+B) is polynomial A - B = (3x³ - 3x²) - (-3x³ + 4x² -2x + 1) = 6x³ - 7x² + 2x - 1
∴ Yes, The result of (A-B) is polynomial A * B = (3x³ - 3x²) * (-3x³ + 4x² -2x + 1)
∴ Yes, The result of (A-B) is polynomial