Question

Show that the following conditions are equivalent:

(a) A is a subset of B.

(b) A intersection B = A

(c) A - B = phai

(d) A union B = B

Answer 1

if A is a subset of B , then all the elements which are in A , is in B also, so A-B=phai

so, all the element of A is in B, so A intersection B =A

and since all elements of A is in B , A union B=B
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