Question

For which operations is the set {–1, 0, 1} closed? Choose all answers that are correct. A. addition B. division C. multiplication D. subtraction

Answer 1

Hello,

Addition : no because -1+(-1)=-2 not in set.
Division : no because 1/0 is not in the set :infinity
Multiplication yes: {-1,0,1}*{-1,0,1}={-1,0,1}
Substraction: No because (-1)-(1)=-2 not in set.

Answer C