if AXA has 9 elements among which are found (-1,0) and (0,1) find set a ?
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Let n(A) = p.
Given that n(A * A) = 9
= > n(A) * n(A) = 9
= > p * p = 9
= > p^2 = 9
= > p = 3.
Clearly, Set A has 3 elements.
Since(-1,0) ∈ A * Aand (0,1) ∈ A * A.
= > (-1,0) ∈ A and 0 ∈ A
= > (0,1) ∈ A and 1 ∈ A
Therefore -1, 0, 1 ∈ A.
Hence A = {-1, 0, 1}.
Therefore remaining elements are :
{-1,-1}, { -1,1}, {0,-1}, {0,0}, {1,-1}, {1,0}, {1,1}.
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51
We know that,
If n(A) = p and n(B) = q, then n(A × B) = pq
From the given,
n(A × A) = 9
n(A) × n(A) = 9,
n(A) = 3 ……(i)
The ordered pairs (-1, 0) and (0, 1) are two of the nine elements of A × A.
Therefore, A × A = {(a, a) : a ∈ A}
Hence, -1, 0, 1 are the elemets of A. …..(ii)
From (i) and (ii),
A = {-1, 0, 1}
The remaining elements of set A × A are (-1, -1), (-1, 1), (0, -1), (0, 0), (1, -1), (1, 0) and (1, 1)
Hope it's Helpful.....:)
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