Ответ:
1.1. x-(x-y) = x-x+y = y
1.2. 3,5x*(-4/7 y) = - 7/2 * 4/7 * xy = -2xy , коэффициент = -2
1.3. -9x+3y+4x+y = -5x + 4y
2.1. -x+y-(y-x) = -x+y-y+x = 0
2.2. 1 2/9 y *(-2,3x) = - 11/9 * 23/10 * yx = - 253/90 * yx = -2 73/90 * yx , коэффициент = -2 73/90
2.3. 3x+4y-4x-(-y) = 3x+4y-4x+y = -x+5y