Question

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

Answer 1

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