(а-b)+(c-d) = а - b + c - d(x+y)-(z+t) = x + y - z - t(m-n)-(k-t) = m - n - k + t(t+s)+(-p-m) = t + s - p - m
(x+y)+(y-x) = x + y + y - x = 2y(a-b)-(a-b) = a - b - a + b = 0(c-d)-(c+d) = c - d - c - d = -2d(u+v)-(v-u) = u + v - v + u = 2u
(а-b)+(c-d) = а - b + c - d
(x+y)-(z+t) = x + y - z - t
(m-n)-(k-t) = m - n - k + t
(t+s)+(-p-m) = t + s - p - m
(x+y)+(y-x) = x + y + y - x = 2y
(a-b)-(a-b) = a - b - a + b = 0
(c-d)-(c+d) = c - d - c - d = -2d
(u+v)-(v-u) = u + v - v + u = 2u