If we have two functions f(x) = 3x - 1 and g(x) = 3x + 4, a number of operations can be performed including addition, subtraction, multiplication and division. Simple addition of the two functions yields f(x) + g(x) = 6x - 3. However subtraction of the two functions yields f(x) - g(x) = -3 which has zero coefficient on the x term and hence is the answer.