Question

CARDINALUL  MULTIMII { x∈ N 15/X+2∈ N}

Answer 1

15/(x+2)∈N    ⇒x+2 | 15⇒  x+2∈ {1,3,5,15}
x∈N

1)x+2=1   x=1-2   x=-1 ∉N

2)x+2=3  x=3-2    x=1 ∈N

3)x+2=5   x=5-2   x=3∈N

4)x+2=15  x=15-2=13 ∈N