Question

formula for n( A-B) ​

Answer 1

Step-by-step explanation:

n(A-B) = n only A = n(A) - n(A intersection B).

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Answer 2

Answer:

   n(A) - n(A ∩ B)  or n(A∪B) - n(B) are the required  formula for n(A-B)

Step-by-step explanation:

Explanation :

Formula for n(A-B ) = n(A) - n(A ∩ B)  or

  n(A-B) = n(A∪B) - n(B)

Proof :

Let two intersecting circles.

Here we have given (A-B ) which means that the elements in A that are

not in B .

Where (A ∩ B) represent  the  common elements in A and B this is called intersection  element  of A and B .

(where symbol  ∩   represent the intersection )

So, Subtract the number of elements that are in both A and B which is

(A ∩ B) form the number of elements in set A .

Therefore , we have

n(A-B ) = n(A) - n(A ∩ B)  and  we can also write this  as

n(A-B) = n(A∪B) - n(B)

proved.

Final answer :

Hence , the formula for n(A-B) = n(A) -  n(A ∩ B) or n(A∪B) - n(B).