Set A contains the element 1. What other whole numbers must be in set A for it to be closed under addition?
For set A to be closed under addition, it must contain all whole numbers that can be obtained by adding 1 to any element already in set A.
In this case, since set A already contains the element 1, to make it closed under addition, it must also contain the whole number that results from adding 1 to 1, which is 2.
Therefore, for set A to be closed under addition, it must contain the elements 1 and 2.
In order for a set to be closed under addition, it means that if you take any two elements from the set and add them together, the result must also be in the set.
Since set A already contains the element 1, let's consider adding 1 to it. If we add 1 to any number, the result will be greater than that number. So, we can conclude that if 1 is in the set, then all numbers greater than 1 must also be included in order for set A to be closed under addition.
Therefore, to make set A closed under addition, it must contain all whole numbers greater than or equal to 1. In other words, set A must be the set of all positive integers (1, 2, 3, 4, ...) or the set of all non-negative integers (0, 1, 2, 3, ...).