If (-1, 2), (2, -1) and (3, 1) are any three vertices of a parallelogram, then

If (-1, 2), (2, -1) and (3, 1) are any three vertices of a parallelogr

1.	If (-1, 2), (2, -1) and (3, 1) are any three vertices of a parallelogram, then
Answer» then what complete question plz.