E(x) = (x+3)²-(2x-1)²+3x(x-3)+1-x
E(x) = x²+6x+9 - (4x²-4x+1)+3x²-9x+1-x
E(x) = 4x²-4x+10-4x²+4x-1
E(x) = 9 care este numar natural.