Answer Happy

Which of the following is a subspace of R³? Justify your answer. i) W = {(x,y,z) |3x+2y+z=0} ii) W = {(x,y,z) | x² + y² + z² = 9} iii) W = {(x, y, z) | x = y + 1} v). W = {(3x,2x,5x) |x is a real number}