Dau coroanaaaaaaaa!!!!!!!!!!!!

Explicație pas cu pas:
(3x+1)|125 =>3x+1€D125 in Z =>
3x+1€{-125,-25,-5,-1,1,5,25,125} =>
3x€{-126,-26,-6,-2,0,4,24,124} =>
x€{-42,-26/3,-2,-2/3,0,4/3,8,124/3}
x€N=>x={0,8}