Question

nr de forma x2x divizibile cu 3

Answer 1

x+2+x ∈M3
2x+2∈{0,3,6,9,12,15,18,21}
2x∈{-2,1,4,7,10,13,16,19}
x∈{-1,1/2,2,7/2,5,13/2,8,19/2}
x∈N,x<9
Din ambele rezulta x∈{2,5,8}