Giải thích các bước giải:
a)-(a-c)-(a-b+c)
= -a+c-a+b-c
=(-a-a)+(c-c)+b
=-2a+0+b
=-2a+b
b)-(a-b+c)-(a+b+c)
=-a+b-c-a-b-c
=(-a-a)+(b-b)+(-c-c)
=-2a+0+-2c
=-2a+-2c
c)(a+b)-(a-b)+(a-c)-(a+c)
=a+b-a+b+a-c-a-c
=(a-a+a-a)+(b+b)+(-c-c)
=0+2b+-2c
=2b+-2c
d)(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+0+0
=2a