A ve B çoxluqları üçün element saylarının tapılması

MathematicsSet TheoryMedium

Published: September 7, 2026

Question

19. $A$ və $B$ çoxluqları üçün $n(A \setminus B) = 7$, $n(B \setminus A) = 5$, $n(A \cup B) = 20$ olarsa, $n(A) + n(B) + n(A \cap B)$-ni tapın.

Animated Video Solution

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Step 1

Hi Elza, let's solve this set theory problem together.

Step 2

Let us define our variables. We have two sets, A and B. Let x be the number of elements in the intersection of A and B.

n(A \cap B) = x

Step 3

We know the number of elements only in A is 7, and only in B is 5. We can express the number of elements in the union as the sum of these parts.

n(A \cup B) = n(A \setminus B) + n(B \setminus A) + n(A \cap B)

Step 4

Substituting the known values, we get 20 equals 7 plus 5 plus x.

$$20 = 7 + 5 + x$$

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