Problem: Which of the following binary operations are closed?
- subtraction of positive integers
- division of nonzero integers
- function composition of polynomials with real coefficient
- multiplication of $2 \times 2$ matrices with real entires
- exponentiation of integers
Solution: I encourage you to attempt to solve the problem today. The solution will be provided tomorrow. This will give you the opportunity to test your understanding of the problem and to improve your skills in solving similar problems in the future.