(1) xy(x = y (y = x)) (2) xyz((x = y & y = z) (x = z)) (3) xyz(x = y ((x emb Z) (y emb Z))
(2) xyz((x = y & y = z) (x = z))
(3) xyz(x = y ((x emb Z) (y emb Z))
(4) x(x = x)
3. See 'Let X = X But Not Necessarily'.