Subtraction of elements in sets
By John Peck •
Let A be a set of finite elements.
$A=\{1,2,3,4,5\}$
If I want to remove one element and show I removed one element, how should I do?
Pseudo mathematical notation:
$A - \{2\} = \{1,3,4,5\}$
Thank you very much!
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$\endgroup$ 61 Answer
$\begingroup$Your notation above is actually used in set theory.
In general if you have two sets $A$ and $B$, the difference $A - B$ is the set
$A - B = \{x \in A : x \notin B\}$
Also, note that $\{1, 2, 3, 4, 5\} - \{2, 6\} = \{1,3,4,5\}$. $B$ need not be a subset of $A$.
$\endgroup$ 1
