d(x, y) = 0 if x=y57 if x, y

d(x, y) = 0 if x=y57 if x, y ∈X− {j}1 if x, y ∈X− {k}47if x, y ∈X− {i}. (x, y) =  1 if x, y ∈X,0 otherwise 

Kết quả (Việt) 1:

d (x, y) = 0 nếu x = y57 nếu x, y ∈X− {j} 1 nếu x, y 47if ∈X− {k} x, y ∈X− {i}. (x, y) =  1 nếu x, y ∈X, 0 nếu không 

Kết quả (Việt) 2:

d (x, y) = 0 nếu x = y57 nếu x, y ∈X- {j} 1 nếu x, y ∈X- {k} 47if x, y ∈X- {i} . (X, y) =  1 nếu x, y ∈X, 0 nếu 