are fractions closed?

[korean]

ok my question is:

are fractions closed?

i think they are but im getting a lot of people telling me im wrong....here is my logic

since a/b - c/b = a-c/b where a,b,c are whole numbers. and since fractions are integers that also includes negative numbers right? if not please correct me and give me an example and/or counterexample.

 

[korean]

also

since a/b - c/d = (ad - bc)/(bd) where a,b,c,d are whole numbers. also works since fractions are integers. so it also includes negative fractions.

 

[tkhunny]

Closed under what conditions or operations?

What is your definition of a fraction? Do you mean "Rational Numbers"?

\(\displaystyle \L\frac{1}{2}\;+\;\frac{1}{2}\;=\;1\)

Is that closed under addition, or not?