Fie a₀ un numar natural. Definim multimea A={[tex]a_{0}, a_{1}, a_{2} , a_{3},.., a_{n},... [/tex]} unde [tex] a_{1}= \sqrt{ a_{0}^2 +1},..., a_{n+1}= \sqrt{ a_{n}^2 +1},.... [/tex]. Aratati ca A-Q≠(multimea vida). Mersi