6a(a - x + c) + 6x(a + x - c) - 6c(a - x - c)= 6a^2 - 6ax + 6ac + 6ax + 6x^2 - 6xc - 6ac + 6cx + 6c^2= 6a^2 + 6x^2 + 6c^2
6a(a - x + c) + 6x(a + x - c) - 6c(a - x - c)
= 6a^2 - 6ax + 6ac + 6ax + 6x^2 - 6xc - 6ac + 6cx + 6c^2
= 6a^2 + 6x^2 + 6c^2