find n(A)for each set

A={1/2, -1/2, 1/3, -1/3,..., 1/10, -1/10}

4 answers

what is n(a set)?
looks like the fractions from 1/2 , 1/3 . ... 1/10 come in pairs with their negatives,
I count 18 of them
n(A) is the cardinal of the sets and how did you get the #18
o ok i got it 1/2 1/3 1/4 1/5 1/6 1/7 1/8 1/9 1/10 thanks