# What does it mean that polynomials are closed under addition?

If you add any two numbers from a set and the resulting number is still part of the set, then the set is considered closed under addition. A mathematical representation of a group with multiple elements is a set. Elements within a set can consist of various mathematical objects, such as numbers, symbols, lines, points in space, geometric structures, variables, or even other sets. A set with a single element is known as a singleton, and a set with no elements is known as an empty set. Sets can be infinite or contain a finite number of items. If two sets have the same number of elements, they are equivalent. Set theory, specifically Zermelo-Fraenkel set theory, has been the foundation of mathematics since the first half of the 20th century. More information on sets can be found at brainly.com/question/24462379 #SPJ4.