A = {x + 12 ; 2x - 3 ; 3x + 5}, B = {2x + 1 ; x + 8 ; 5x - 17}, x = ?, x ∈ N, a. i.
A = B.
A = B daca: x + 12 = 2x + 1, 12 = x + 1, x = 11
2x - 3 = x + 8, x - 3 = 8, x = 11
3x + 5 = 5x - 17, 5 = 2x - 17, 2x = 5 + 17, 2x = 22, x = 11.
Deci x = 11 este nr. cautat.