Упрости выражения (17.1-17.2).

17.1. 1) $(x^8 - 2)(x^4 - 1) - x^{12} + 2x^4 = x^{12} - x^8 - 2x^4 + 2 - x^{12} + 2x^4 = -x^8 + 2$ 3) $(x^{15} + 5)(x^3 + 2) - 10 - x^{18} = x^{18} + 2x^{15} + 5x^3 + 10 - 10 - x^{18} = 2x^{15} + 5x^3$ 17.2. 1) $0.5a^2c^4(a^4 - c^2 + 6) - 0.5a^6c^4 - 0.5a^2c^6 = 0.5a^6c^4 - 0.5a^2c^6 + 3a^2c^4 - 0.5a^6c^4 - 0.5a^2c^6 = -a^2c^6 + 3a^2c^4$ 2) $4.8x^8y^7 - (12x^8y^5 - 6) - 2.4x^6y^5(2x^2y^2 - 5y + 3) = 4.8x^8y^7 - 12x^8y^5 + 6 - 4.8x^8y^7 + 12x^6y^6 - 7.2x^6y^5 = -12x^8y^5 + 12x^6y^6 - 7.2x^6y^5 + 6$ 3) $2.5t^8s^{10}(4t^2 - 6c^2 - 3) + 15t^8c^2s^{10} - 10t^{10}s^{10} = 10t^{10}s^{10} - 15t^8c^2s^{10} - 7.5t^8s^{10} + 15t^8c^2s^{10} - 10t^{10}s^{10} = -7.5t^8s^{10}$ 4) $9a^{20}b^{16} - 1.8a^{10}b^{18} - 0.9a^5b^9(10a^{15}b^7 + 2a^5b^9) = 9a^{20}b^{16} - 1.8a^{10}b^{18} - 9a^{20}b^{16} - 1.8a^{10}b^{18} = -3.6a^{10}b^{18}$