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 A - 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, A - C = {3, 6, 9, 12, 15, 18, 21} - {2, 4, 6, 8, 10, 12, 14, 16}
here, you can see that 6, 12 are present in both the sets so, A - C will not contain 6, 12 and will contain rest of element A.
so, A - C = {3, 9, 15, 18, 21}

Answer 2

Solution :

Given A = { 3,6,9,12,15,18,21 }

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

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

= { 3,6,9,12,15,18,21 } - { 2,4,6,8,10,12,14,16 }

= { 3,9,15,18,21 }

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