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A natural number is a number that occurs commonly and obviously in nature. As such, it is a whole, non-negative number. The set of natural numbers, denoted N, can be defined in either of two ways: N = {0, 1, 2, 3, ...}
As per given option.
(a) As no odd natural number is divisible by 2, the set A is empty.
(b) Since no natural number satisfies the equation x + 5 = 0,
? B = ?
(c) Since 2 is an even prime number, i.e., C = {2}, C is not an empty set.
(d) Since there is no natural number between 1 and 2, D is an empty set.
(a) A = { x : x ? Z and x2 ? 2x ? 3 = 0} = {3, -1}.
? A is a finite set.
(b) B = The set of natural numbers divisible by 2 = { 2, 4, 6, 8, 10,?}.
? B is an infinite set.
(c) Since infinite number of lines pass through a point, C is an infinite set.
(d) D = { -4, -3, -2,?}. Clearly D is an infinite set.
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B = {5, 10, 15,?}
C = {10, 20, 30,?}
B ? C = {5, 10, 15,?} ? {10, 20, 30,?}
B ? C = {5, 10, 15,?}
? A ? (B ? C) = {2, 4, 6,?} ? {5, 10, 15,?} = {10, 20, 20,?} = C.
A ? B is a set of member which belong to A but do not belong to B
? A ? B = {3, 5, 7, 9, 11} - {7, 8, 9, 10, 11}
A ? B = {3, 5}
According to formula,
(A ? B)? = U - (A ? B)
? (A ? B)? = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11} - {3, 5}
(A ? B)? = {2, 4, 6, 7, 8, 9, 10, 11}.
Given in the question,
n(S) = 21, n(T) = 32, n(S ? T) = 11, n(S ? T) = ?
Using the formula,
n(S ? T) = n(S) + n(T) ? n(S ? T) = 21 + 32 ? 11 = 42
Hence, S ? T has 42 elements.
A × B = {1, 2} × {2, 3}
= {(1, 2), (1, 3), (2, 2), (2, 3)}.
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