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9.Determinati x apartine lui N,stiind ca:
a) x|(x+3)
b) x| (3x+5)
c)(x+1) | (x+7)


Răspuns :

a) x | (x+3)
x | x rezulta x | (x+3-x)
x | 3
[tex]x\in\{1,3\}[/tex]
b) x | (3x+5)
x | 3x rezulta x | (3x+5-3x)
x | 5
[tex]x\in\{1,5\}[/tex]
c) (x+1) | (x+7)
(x+1) | (x+1) rezulta (x+1) | 6
[tex]x+1\in\{1,2,3,6\}[/tex]
[tex]x\in\{0,1,2,5\}[/tex]