Answer: factors.
Explanation: The expression: 25x^2 - 81 is a quadratic equation, so it has two x-axis intercepts.
Now, it can be written as (5x - 9)(5x + 9) = 5(x - 9/5)(x + 9/5)
where -9/5 and 9/5 are the two x-axis intercepts of the quadratic equation.
Now, the equation (5x - 9)(5x + 9) is called a "factorization" of the equation 25x^2 - 81, and the segments (5x - 9) and (5x + 9) are called "factors" of the equation 25x2 - 81.