a) \[(x^2 + xy - y^2)(x + y) = x^3 + x^2y + x^2y + xy^2 - xy^2 - y^3 = x^3 + 2x^2y - y^3\]
б) \[(n^2 - np + p^2)(n - p) = n^3 - n^2p - n^2p + np^2 + p^2n - p^3 = n^3 - 2n^2p + 2np^2 - p^3\]
д) \[(a^2 - 2a + 3)(a - 4) = a^3 - 4a^2 - 2a^2 + 8a + 3a - 12 = a^3 - 6a^2 + 11a - 12\]
e) \[(5x - 2)(x^2 - x - 1) = 5x^3 - 5x^2 - 5x - 2x^2 + 2x + 2 = 5x^3 - 7x^2 - 3x + 2\]