Question

Suppose u and v both denote sets in Python. Under what condition can we guarantee that u - (v - u) == u?
This is true for any u and v.
The set u should be a subset of v.
The set v should be a subset of u.
The sets u and v should be disjoint.

Answer 1

yes it is true for any u and v

Answer 2

The set v should be a subset of u. In order to make the condition u-(v-u)==u as TRUE and with the given condition u and v both denote sets in Python. The given statement can be set true when the set v is a subset of u. For example,

u = { 1,2,3 }

v = { 1, 2 }

Then u -v = {3}

then u - (u -v) = { 1, 2 }  which is equal to v . Hence it is proved.