(2x + 1) ∈ D7 2x + 1 ∈ {1,7} 2x ∈ {0,6} x ∈ {0,3)
(3x+1) ∈ D16 3x + 1 ∈{1,2,4,8,16} 3x ∈ {0,1,3,7,15} x ∈ {0,1,5}
(6x+5) | 30 (6x + 5)∈ D30 (6x+5) ∈ { 1,2,3,5,10,15,30}
6x ∈ { -4,-3,0,5,10,25} x = 0
(2x + 1) | 35 (2x + 1)∈ {1,5,7,35} 2x∈{0,4,6,34} x ∈ {0,2,3,17}
2ˣ | 3ˣ x = 0
4ˣ | 5ˣ + 2014 U cifra (5ˣ + 2014) = 9 ⇒ (5ˣ + 2014 ) nu este divizibil cu 2 sau cu 4 x = 0 1 | 2015
5ˣ | 4ˣ + 1 5ˣ si 4ˣ sunt numere prime intre ele x = 0 ⇒ 1 | 2
2013 | (2012ˣ + 1) x = 1
