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 D - A

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}.

∴ D – A = {5, 10, 15, 20} - {3, 6, 9, 12, 15, 18, 21}
here , you can see that 15 is present in both the sets so, D – A won't contain 15 but it will contain rest elements of D.

hence, D – A = {5, 10,20}

Answer 2

Solution :

Given

D = { 5,10,15,20 }

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

D-A={ x:x€D and x doesn't belongs A }

= { 5,10,15,20 } - { 3,6,9,12,15,18,21 }

= { 5,10,20 }

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