In short, contradiction is the unity of opposites. The opposite attribute of contradiction is struggle, and the unified attribute of contradiction is the same, which are two basic attributes inherent in contradiction.
Mathematical explanation: for example, Y= 10000_X, because the sum of x and y is always 10000, so x decreases and y inevitably increases, and x increases and y inevitably decreases. So this formula can use x and y to represent the contradiction between two things.