Voi rezolva inecuatia |(3n+1)/(n-3)|>1/5 in N.
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|(3n+1)/(n-3)|>1/5 <=> (3n+1)/|n-3|>1/5 ...(*)
Daca n<3: (*) <=> (3n+1)/(3-n)>1/5 <=> 15n+5>3-n <=> 16n>-2 <=> n>-1/8, adevarat. => n=0, n=1 si n=2 sunt solutii.
Daca n>3: (*) <=> (3n+1)/(n-3)>1/5 <=> 15n+5>n-3 <=> 14n>-8 <=> n>-4/7, adevarat. => orice n apartine N, n>3 este solutie.
Pe baza celor doua cazuri discutate obtinem S=N\{3}.
