In 1-2 sentences, explain why following operation is a closed system under subtraction.

The operation defined by subtracting the polynomial \( (2x^2 + 12x + 11) \) from \( (9x^2 + 17x + 13) \) is a closed system under subtraction because the result, \( (9x^2 + 17x + 13) - (2x^2 + 12x + 11) = 7x^2 + 5x + 2 \), is also a polynomial, which remains within the same set of polynomials. Thus, the set of all polynomials is closed under the operation of subtraction.