Question

Determina numarul natural x , astfel incat 18 supra 2x+1 apartine N

Answer 1

18 /(2x +1) ∈ N  ⇔  (2x + 1) ∈ D18    2x + 1 ∈ {1,2,3,6,9,18}
2x ∈ { 0,1,2,5,8,17}    ⇒ x ∈ { 0,1,4}

Answer 2

18/2x+1∈N⇒2x+1∈D18
D18∈{1,2,3,6,9,18}

1. 2x+1=1
    2x=1-1
    2x=0
    x=0:2
    x=0

2. 2x+1=3
    2x=3-1
    2x=2
    x=2:2
    x=1

3. 2x+1=9
    2x=9-1
    2x=8
    x=8:2
    x=4