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a fost răspuns

det nr nat x astfel incat 18 supra 2x+1, x=?

Răspuns :

Icecon2005
banuiesc ca asa arata ecuatia : 18/(2x +1)=0
9/x+18=0
9/x=-18
x= - 2
 
Fractia [tex] \frac{18}{2x+1} [/tex] ∈ N ⇔ 2x+1 | 18
2x+1 ∈ {1,2,3,6,9,18}
2x ∈ {0,1,2,5,8,17}
x ∈ {0, 1/2, 1, 5/2, 4, 17/2}
Dar din enunt x ∈ N
Deci in final x ∈ {0, 1, 4}.

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