A) 6a^2 - 3a + 1 + 6a^2 - 1 = 12a^2 - 3a = 3a(4a - 1)
6a^2 - 3a + 1 - 6a^2 + 1 = 2 - 3a
б) n^3 + 2n^2 - n + 1 + 1 - n^3 = 2n^2 - n + 2
n^3 + 2n^2 - n + 1 - 1 + n^3 = 2n^3 + 2n^2 - n
в) k^3 - 3k^2 + 1 + 2k^3 - 3k^2 + 4 = 3k^3 - 6k^2 + 5
k^3 - 3k^2 + 1 - 2k^3 + 3k^2 - 4 = - k^3 - 3
г) 3x^2 - 2x + 7 + 2x^2 + 2x + 7 = 5x^2 + 14
3x^2 - 2x + 7 - 2x^2 - 2x - 7 = x^2 - 4x