а) (а-в)^2=(в-а)^2
(a-b)^2={-(b-a)}^2=(-1)^2(b-a)^2=(b-a)^2
б) (х+у)^2=(-х-у)^2
(x+y)^2={-(-x-y)}^2=(-1)^2(-x-y)^2=(-x-y)^2
а) (а-в)^2=(в-а)^2
(a-b)^2={-(b-a)}^2=(-1)^2(b-a)^2=(b-a)^2
б) (х+у)^2=(-х-у)^2
(x+y)^2={-(-x-y)}^2=(-1)^2(-x-y)^2=(-x-y)^2