Question

Multimea A verifica simultan relatiile:
a) 3 apartine A;
b) daca n apartine A, atunci 4 n apartine A;
c) daca 2 n + 14 apartine A, atunci n apartine A.
Aratati ca numarul 17 apartine multimii A

Answer 1

deoarece 3∈A => 4*3=12∈A =>4*12=48∈A
Dar conf  3 Daca 48∈A =>2n+14=48=>2n=34=>n=17 QED