let u={a,b,c,d,e,f,g,h,i,j,k} A= {a,b,c,d,e,f} B= {a,g,i,j,k} C={e,h,j}

Question

What is 

 

BUC

 

A-B

 

(A-B)-C

 

 

 

 

Answer 1

BUC is the union of the two sets B and C. The union contains all the elements that belong to B or C (or both). So in this case, it would be (a,g,i,j,k,e,h)

 

A-B is a modification of a set by removing the elements of B from the set A. So A-B={b,c,d,e,f)

While (A-B)-C= {b,c,d,f}

 

In general if you have two sets A and B, the difference A−B is the set

A−B={x∈A:x∉B}