In 1–2 sentences, explain why the following operation is a closed system under subtraction. (9x^2+17x+13)−(2x^2+12x+11) (2 points)

The operation is a closed system under subtraction because subtracting two polynomials results in another polynomial of the same degree, ensuring that the set of polynomials is preserved. Specifically, the result of \( (9x^2 + 17x + 13) - (2x^2 + 12x + 11) \) is again a polynomial, \( 7x^2 + 5x + 2 \), demonstrating closure under this operation.