2x - 1 = 7
2x = 7 + 1
2 x = 8
x = 8 : 2
x = 4
Verific : 2 × 4 - 1 = 7 care e divizibil cu 7
(2x-1) I 7
2x-1 =7 => 2x = 8 => x = 4
Generalizind , x = 4k (multiplu de 4) ; unde k ∈ N
2x-1 = -7 => x = -3 ; x = - 3k (multiplu de -3) ; unde k ∈ N
