Final answer:
Polynomials form a closed system under both addition and subtraction, meaning the result will always be another polynomial. The basic principle is combining like terms, observing the order of operations and the signs of coefficients.
Step-by-step explanation:
Polynomials are a closed system under addition and subtraction, just as whole numbers and integers are. This means that when you add or subtract polynomials, the result is always another polynomial. The basic principle in working with addition and subtraction is to combine like terms while paying attention to the signs of the coefficients. When working specifically with whole numbers, you pay attention to maintaining the properties of closure, commutativity (e.g. A + B = B + A), and associativity.
As an example, when adding the polynomials (2x2 + 3x + 1) and (x2 - 4x + 5), you combine like terms to get another polynomial: 3x2 - x + 6. Similarly, subtracting (x - 3) from (2x2 + x + 1) results in the polynomial 2x2 - 2. The resulting expressions following these operations remain as polynomials, not turning into integers or any other type of number.