Bỏ dấu ngoặc rồi thu gọn biểu thức sau:
a) (a+b)-(a-b)+(a-c)-(a+c)
=a+b-a+b+a-c-a-c
=2b-2c
=2(b-c)
b) (a+b-c)+(a-b+c)-(b+c-a)-(a-b-c)
=a+b-c+a+b-c-b-c+a-a+b+c
=3a+3b-3b
=3(a+b-c)
a)
(a+b)-(a-b)+(a-c)-(a+c)
=a+b-a+b+a-c-a-c
=(a-a+a-a)+(b+b)+(-c-c)
=2b-2c.
b)
(a+b-c)+(a-b+c)-(b+c-a)-(a-b-c)
=a+b-c+a-b+c-b-c+a-a+b+c
=(a+a+a-a)+(b-b-b+b)+(-c+c-c+c)
=2a