[tex] \frac{1}{10} \ \textless \ \frac{10}{x} \ \textless \ \frac{1}{9} [/tex]
O sa luam pe cazuri:
I [tex] \frac{1}{10} \ \textless \ \frac{10}{x} \\ x \ \textless \ 100[/tex]
II [tex] \frac{10}{x} \ \textless \ \frac{1}{9} \\ x \ \textgreater \ 90[/tex]
Facem intersectia celor doua si o sa obtinem:
x ∈ (-∞;100)
x ∈ (90;+∞) ⇒ x ∈ (90;100)
Tinand cont ca x ∈ IN* ⇒ x ∈{91; 92; 93; 94; 95; 96; 97; 98; 99}
