= 2y
= 0
= -2d
=2u
а) (x+y)+(y-x)=x+y+y-x=2y
б) (a-b)-(a-b)=a-b-a+b=0
в) (c-d)-(c+d)=c-d-c-d=-2d
г) (u+v)-(v-u)=u+v-v+u=2u
= 2y
= 0
= -2d
=2u
а) (x+y)+(y-x)=x+y+y-x=2y
б) (a-b)-(a-b)=a-b-a+b=0
в) (c-d)-(c+d)=c-d-c-d=-2d
г) (u+v)-(v-u)=u+v-v+u=2u