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

    =  a+ b – c + d  + a + b -  c + d

    = 2a + 2b + 2d – 2c  

a: =a-b-d+b-a+d=0

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

=  a+ b – c + d  + a + b -  c + d

= 2a + 2b + 2d – 2c

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

= a+ b – c  +  a – b  –  a + b +  c

= a + b

Bài làm 

\(a\left(b-c-d\right)-b\left(c+a\right)=ab-ac-ad-bc-ba\)

\(=-ac-ad-bc\)

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

=a.b-a.c-a.d-b.c-b.a

= -a.c-c.d-b.c

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

\(=ab-ac-ad-bc-ba\)

\(=\left(ab-ba\right)-ac-ad-bc\)

\(=-ac-ad-bc\)

Học tốt

D

A

nếu như mình làm sai thì đừng xóa nhé:T

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

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

=0+0+3c-d

=3c-d

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

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

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

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

Vay = -2a+3c+d+2b

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

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

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

=-2a+3c+(-d)-2b

Bài 4: 

b: \(=x^2z\left(-1+3-7\right)=-5x^2z=-5\cdot\left(-1\right)^2\cdot\left(-2\right)=10\)

c: \(=xy^2\left(5+0.5-3\right)=2.5xy^2=2.5\cdot2\cdot1^2=5\)

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

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

\(=2b-2c\)

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

\(b,\) Thay \(a=5,b=7,c=8\) vào biểu thức

\(\Rightarrow\left(5+7-8\right)-\left(5-7+8\right)=-2\)