Is the equation $x+y+z=0$ the xyz-plane ?(i.e.

Is the equation $x+y+z=0$ the xyz-plane?(i.e.

Is the equation $x+y+z=0$ the xyz-plane?

(i.e. points that are multiples of $(1,1,1)$)

(i.e. points that are multiples of $(1,1,1)$)