Vector Space, Topological Space, Mathematics, Math, Linear Algebra.
belongs to S or { } ∪ {1} = {1} which belongs to S. (DONE) Check 3: { } ∩ {1, 3, 6} = { } which belongs to S or {1} ∩ {1, 3} = {1} which also belongs to S or {1, 3} ∩ {1, 3, 6} = {1, 3} which belongs to S. (DONE) Hence, the collection of all 4 open sets, S = {{ }, {1}, {1, 3}, {1, 3, 6}} forms a