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 + 0 + 0 - 2d

= -2d

Ý b, c em xem lại xem sao chỗ chữ cái viết hoa chỗ lại viết thường là sao em nhỉ?

Cô oi chữ nó bị thế thoi, A và a giống nhau cô ah

a) \(\left(a+b-c\right)-\left(b-c+d\right)\)

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

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

\(=a-d\)

b) \(-\left(a-b+c\right)+\left(a-b+d\right)\)

\(=\left(-a\right)+b-c+a+b-d\)

\(=\left(-a\right)+a+b+b-c-d\)

\(=2b-c-d\)

c) \(\left(a+b\right)-\left(-a+b-c\right)\)

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

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

\(=2a+c\)

d) \(-\left(a-b-c\right)+\left(a-b-c\right)\)

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

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

\(=2b+2c\)

(chắc hơi sai... > . < ...)

Giải:

\(A=\left(a+b\right)-\left(a-b\right)+\left(a-c\right)-\left(a+c\right)\)

\(\Leftrightarrow A=a+b-a+b+a-c-a-c\)

\(\Leftrightarrow A=\left(a-a+a-a\right)+\left(b+b\right)+\left(-c-c\right)\)

\(\Leftrightarrow A=2b-2c\)

\(\Leftrightarrow A=2\left(b-c\right)\)

Vậy ...

a)

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

A = a + b - a + b + a- c - a - c

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

= 2b -2c

1: =a-b+c-a-c=-b

2: =a+b-b+a+c=2a+c

3: =-a-b+c+a-b-c=-2b

4: =ab+ac-ab-ad-ac+ad=0

A=a+b-a+b+a-c-a-c=a+2b-2c

B=a+b-c+a-b+c-b-c+a-a+b+c=2a

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

`=a+b-a+b+a-c-a-c`

`=2b-2c`

b) `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`

`=2a`

\(A=\left(a+b\right)-\left(a-b\right)+\left(a-c\right)-\left(a+c\right)\)

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

\(A=2b-2c\)

\(B=\left(a+b-c\right)+\left(a-b+c\right)-\left(b+c-a\right)-\left(a-b-c\right)\)

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

\(B=2a\)

a)(a+b)-(a-b)+(a-c)-(a+c) 

=a+b-a+b+a-c-a-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

=2a

Giải:

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

    A=a+b-a+b+a-c-a-c

    A=0+(a-a)-c-c

    A=0+0-c-c

    A=-c-c

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

    B=a+b-c+a-b+c-b-c+a-a+b+c

    B=(a+a+a-a)+(b-b-b+b)+(-c+c-c+c)

    B=(a+a)+0+0

    B=a+a

Chúc bạn học tốt!

A= ( a - b) - ( a - b -c ) - ( 2a + c - a)

\(=a-b-a+b+a-2a-c+a\)

\(=\left(a-a+a+a-2a\right)+\left(-b+b\right)+c\)

\(=\left(2a-2a\right)+c\)

\(=c\)

A = (a - b) - (a - b - c) - (2a + c - a)

\(=a-b-a+b+c-2a-c+a\)

\(=\left(a-a+a+a-2a\right)+\left(-b+b\right)+c\)

\(=\left(2a-2a\right)+0+c\)

\(=c\)