Question

lf A= {3, 6, 9, 12, 15, 18, 21} , B={4, 8, 12, 16, 20 }, C={2, 4, 6, 8, 10, 12, 14, 16} D={5, 10, 15, 20}; Find B - C

Answer 1

concept :- A - B shows the relative complement of the set, which represents members of set A which are not part of set B. see figure , here shaded region is shown, this shaded region indicates A - B.

here, A= {3, 6, 9, 12, 15, 18, 21},
B={4, 8, 12, 16, 20 },
C={2, 4, 6, 8, 10, 12, 14, 16},
D={5, 10, 15, 20}.

so, B - C = {4, 8, 12, 16, 20} - {2, 4, 6 , 8 , 10, 12, 14, 16}
here you can see that 4, 8, 12, 16 are present in both the sets. so, B - C won't contain 4, 8, 12 and 16. but it will contain rest elements of B.

hence, B - C = {20}

Answer 2

Solution :

Given

B = { 4,8,12,16,20 }

C = { 2,4,6,8,10,12,14,16 }

B-C = { x:x€B and x doesn't belongs C}

= { 4,8,12,16,20 } - { 2,4,6,8,10,12,14,16 }

= { 20 }

••••