a=x-y, b=y-z, c=x+y
a+b+c = х-у + у-z+ x+y = 2x-z
a=x-y, b=y-z, c=x-z
a-b-c=x-y -(y-z) -(x-z) =x-y -y+z -x+z= -2y +2z=2(z-y)
1) x-y+y-z+x+y=x-z+x+y=2x+y-z
2) x-y-y-z-x-z= -y-y-z-z=-2y-2z=-2(y+z)
a=x-y, b=y-z, c=x+y
a+b+c = х-у + у-z+ x+y = 2x-z
a=x-y, b=y-z, c=x-z
a-b-c=x-y -(y-z) -(x-z) =x-y -y+z -x+z= -2y +2z=2(z-y)
1) x-y+y-z+x+y=x-z+x+y=2x+y-z
2) x-y-y-z-x-z= -y-y-z-z=-2y-2z=-2(y+z)