Given A = {1, 2, 3, 4, 5} and B = {4, 5, 6, 7}. Only the elements which are in A but not in B should be taken.

A – B = {1, 2, 3, 4, 5} – {4, 5, 6, 7} = {, , }

∴ A – B = {, , }. Since 4, 5 are the elements in B they are taken away from A.

Similarly for B – A, the elements which are only in B are taken.

B – A = {4, 5, 6, 7} – {1, 2, 3, 4, 5} = {, }

∴ B – A = {, } (4, 5 are the elements in A and so they are taken away from B).

Note that A – B ≠ B – A

The Venn diagram of A – B and B – A are shown below.