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