Daca 45|(2n+1) => 2n+1 este multiplu de 45
=> 2n+1∈{0, 45, 90, 135, 180...}
daca 2n+1=0 => n∉N
daca 2n+1=45 => 2n=45-1 => 2n=44 => n=44:2 => n=22 , 0≤22≤89;
daca 2n+1=90 => 2n=90-1 => 2n=89 => n∉N
daca 2n+1=135 => 2n=134 => n=67 , 0≤67≤89.
urmatoarele valori nle lui n nu mai convin
=> n∈{22, 67}