Question

For each of the following sets, determine whether{ 2} is an element of that set. a) {x ∈ R | x is an integer greater than 1} b) {x ∈ R | x is the square of an integer} c) {2,{2}} d) {{2},{{2}}} e) {{2},{2,{2}}} f ) {{{2}}}

Answer 1

Sets in a) and b) contain only numbers, thus, they can not have the set {2} as an element. Sets c), d), e) indeed contain {2}. Set f) contain {{2}}, which is not the same as {2}.

Answer. c), d), e).