(х+у-z)-(x+у-z),

(а+b-c)+2,

a+(b-c),

a-(a-b+c),

(x-y)-(x-y),

(a-b+1)-(a+b-1),

(х+у-z)-(x+у-z)= x+y-z-x-y+z= 0

(а+b-c)+2 = a+b-c+2

a+(b-c) = a+b-c

a-(a-b+c) = a-a+b-c = b-c

(x-y)-(x-y) = x-y-x+y = 0

(a-b+1)-(a+b-1) = a-b+1-a-b+1 = -2b+2

1) x+y-z-x-y+z=0

2)a+b-c+2

3) a+b-c

4) a-a-b+c=c-b

5) x-y-x+y=0

6) a-b+1-a-b+1=b+2

Объяснение: