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18
________ x-nr natural
2x+1


Răspuns :

18/2x+1∈N↔2x+1I18
=>2x+1∈D₁₈
D₁₈={1; 2; 3; 6; 9; 18}
2x+1=1=>x=0
2x+1=2=>x=1/2=0,5∉N (nu convine)
2x+1=3=>x=1
2x+1=6=>x=5/2=2,5∉N (nu convine)
2x+1=9=>x=4
2x+1=18=>x=17/2=8,5∉N (nu convine)
x∈{0; 1; 4}