$(x^2 + y^2 + x + y)(x + y + xy) = x^3 + xy^2 + x^2 + xy + x^2y + y^3 + xy + y^2 + x^3y + xy^3 + x^2y + xy^2 = x^3 + 2xy^2 + x^2 + 2xy + 2x^2y + y^3 + y^2 + x^3y + xy^3$

$(2a^2bc - 3b^2c - 7bc^2)(a^2c - b^3c^2 + 3bc^3 - 8c^2) = 2a^4bc^2 - 3a^2b^2c^2 - 7a^2bc^3 - 2a^2b^4c^3 + 3b^5c^3 + 7b^4c^4 + 6a^2b^2c^4 - 9b^3c^4 - 21b^2c^5 - 16a^2bc^3 + 24b^2c^3 + 56bc^4$

$(m^2 - mn^2 - mn - n^2)(m - mn - n^2 + n) = m^3 - m^2n^2 - m^2n - mn^2 - m^3n + m^2n^3 + m^2n^2 + mn^3 - m^2n^2 + mn^4 + mn^3 + n^4 + m^2n - mn^3 - mn^2 - n^3 = m^3 - 2mn^2 - m^3n + m^2n^3 + mn^3 - m^2n^2 + mn^4 + n^4 - n^3$

$(0,1p^3 - 2p^2q - 0,5pq^2 + 1,2p^3)(8p^2 - 0,2pq + 5q^2) = (1,3p^3 - 2p^2q - 0,5pq^2)(8p^2 - 0,2pq + 5q^2) = 10,4p^5 - 16p^4q - 4p^3q^2 - 0,26p^4q + 0,4p^3q^2 + 0,1p^2q^3 + 6,5p^3q^2 - 10p^2q^3 - 2,5pq^4 = 10,4p^5 - 16,26p^4q + 2,9p^3q^2 - 9,9p^2q^3 - 2,5pq^4$