a)-a-b+a+c
b)-a+c-a+b-c
c)b-b-a+c
d)-a+b-c-a-b-c
e)a+b-a+b+a-c-a-c
g)a+b-c+a-b+c-b-c+a-a+b+c
a) -a -( b - a - c ) = -a - b + a + c = - b + c
b) - ( a - c ) -( a - b + c ) = -a + c - a + b - c = - 2a + b
c) b - ( b + a - c ) = b - b - a + c = - a + c
d) - ( a - b + c ) - ( a + b+ c)= - a + b - c - a - b - c = - 2a - 2c
e) ( a + b ) - ( a -b ) + ( a -c ) - ( a + c ) = a + b - a + b + a - c -a - c = 2b - 2c
g) ( a + b - c ) + ( a - b + c ) - ( b + c - a ) - ( a - b -c )
= a + b - c + a - b + c - b - c+ a-a + b + c
= 2a
Nhìn ko hiểu mà lại còn rối nữa???