thanks for reply. I get the last part, but i have trouble to interpret it.
this is what i have done so far:
because x+y+z=0 so y=-(x+z)
because the standard basis for R^3 is (1,0,0) (0,1,0) (0,0,1)
so (x,y,z)=(x,-(x+z),z)=(1,0,0)x-(0,1,0)(x+z)+(0,0,1)z=(1,-1,0)x+(0,-1,1)z
but the numbers...