2x+ 3 trebuie sa divida pe 15 ca sa aiba sens fractia, x apartine Z
Deci D15 = {0,1,3,5,15}
2x+3 = 0 => 2x = -3 => x = -3/2 nu apartine Z
2x+3 = 1 => 2x= -2 => x = -1 apartine Z
2x+3 = 3=> 2x = 0=> x= 0 apartine Z
2x+3 =5=> 2x = 2=> x= 1 apartine Z
2x+3 =15=> 2x= 12 => x= 6 aaprtine Z
deci x={-1,0,1,6}
