308. Упростите выражение: 1) (5a⁴ + 3a²b - b³) - (3a⁴ - 4a²b - b²); 2) (12xy - 10x² + 9y²) - (-14x² + 9xy - 14y²); 3) (7ab² - 8ab + 4a²b) + (10ab - 7a²b); 4) (2c² + 3c) + (-c² + c) - (c² + 4c - 1).

1) $$ (5a^4 + 3a^2b - b^3) - (3a^4 - 4a^2b - b^2) = 5a^4 + 3a^2b - b^3 - 3a^4 + 4a^2b + b^2 = 2a^4 + 7a^2b - b^3 + b^2 $$ 2) $$ (12xy - 10x^2 + 9y^2) - (-14x^2 + 9xy - 14y^2) = 12xy - 10x^2 + 9y^2 + 14x^2 - 9xy + 14y^2 = 3xy + 4x^2 + 23y^2 $$ 3) $$ (7ab^2 - 8ab + 4a^2b) + (10ab - 7a^2b) = 7ab^2 - 8ab + 4a^2b + 10ab - 7a^2b = 7ab^2 + 2ab - 3a^2b $$ 4) $$ (2c^2 + 3c) + (-c^2 + c) - (c^2 + 4c - 1) = 2c^2 + 3c - c^2 + c - c^2 - 4c + 1 = 1 $$