discrete math
posted by thisha .
1. let A and B be sets. Show that
A U (B  A)=A U B
2. determine whether f is a function from Z to R if
a) f(n)= +n
b) 1/(n square 4)
For 1. BA is the same as B intersect ~A (That's the complement of A)
So A U B = A U (B int ~A) = (A U B) int (A U ~A) A U ~A is the universal set.
For 2. a) f(n) is the absolute value function, so yes, it's a function.
For 2. b) 1/(n^2  4) f is not defined at +/ 2
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