Question

Determinati xeN astfel încât :
A) 15 supra x+2 eN
B) 17 supra 2x-1 eN pls

Answer 1

► Punct a:

$\frac{15}{x+2} \in N \implies x+2 \in D_{15}, deci\\\\x+2 \in \{1,3,5,15\} \implies x\in\{-1,1,3,13\} [*]\\\\x\in N [**]\\\\Din\ [*]\ si \ [**] \implies x\in \{1,3,13\}$

► Punct b:

$\frac{17}{2x-1} \in N \implies 2x-1 \in D_{17}, deci\\\\2x-1 \in \{1,17\} \implies 2x \in \{2,18\} \implies x \in \{1,9\} \subset N$