Explicație pas cu pas:
[tex]\frac{18}{2n+1}[/tex]∈Z⇒2n+1∈ D₁₈⇒2n+1∈{±1,±2,±3,±9,±18}
2n+1=1⇒2n=0⇒n=0
2n+1=(-1)⇒2n=-2⇒n=-1
2n+1=2⇒2n=1⇒n=[tex]\frac{1}{2}[/tex]∉Z
2n+1=(-2)⇒2n=(-3)⇒n=(-[tex]\frac{3}{2}[/tex])∉Z
2n+1=3⇒2n=2⇒n=1
2n+1=(-3)⇒2n=(-4)⇒n=(-2)
2n+1=9⇒2n=8⇒n=4
2n+1=(-9)⇒2n=(-10)⇒n=(-5)
2n+1=18⇒2n=17⇒n=[tex]\frac{17}{2}[/tex]∉Z
2n+1=(-18)⇒2n=(-19)⇒n=[tex]\frac{-19}{2}[/tex]∉Z
