B1:

a,  a+b+(-a)+b+a+(-c)+(-a)+(-c)=[a+(-a)+a+(-a)]+(b+b)+[(-c)+(-c)]=0+2.b+(-2).c

b,  a+b+(-c)+a+(-b)+c+(-b)+(-c)+a+(-a)+b+c=[a+a+a+(-a)]+[b+(-b)+(-b)+b]+[(-c)+c+(-c)+c]=2.a+0+0=2a

B2:

N=(a+b)-(a-b)+(a+b)=a+b+(-a)+b+a+b=[a+(-a)+a)+(b+b+b)=a+3.b

NẾU CẬU KHÔNG HIỂU THÌ CỨ HỎI NHÉ!

rút gọn biểu thức

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

b,B=-(a+b+c)-(a+b-5)

uk nha bạn

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

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

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

= 0 + b + c + b + c

= ( b + c ) x 2

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

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

= [ a + a + ( -a ) ] + [ b + ( -b ) + b ] + [ ( -c ) + c ]

= a + b + 0

= a + b

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

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

= [ ( -a ) + ( -a ) + a ] + [ b + b + ( -b ) ] + [ c + ( -c ) + ( -c ) ]

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

a , ( a + b + c ) - ( a - b - c )

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

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

= 0 + b + b + c + c 

= 0 + 2b + 2c

= 0 + 2(b + c )

= 2(b+c)

b , ( a + b - c ) + ( a - b ) - ( a -  b - c )

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

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

= 0 + b + b + 0

= 2b

c , - ( a - b - c ) + ( - a + b - c ) - ( - a + b + c )

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

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

= 0 + 0 + 0 + a + b= a + b

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

a) (a+b)-(a-b)+(a-c)-(a+c)=a+b+a+b+a-c+a-c=(a+a+a+a)+(b+b)+(-c-c)=4a+2b+2*-c

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

                                                                                          =4a+2b+ -c

a,(a+b)-(a-b)+(a-c)-(a+c)

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

=2b+2(-c)

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) a+b-a+b+a-c-a-c

=.........................bạn tự đơn giản biểu thức nhé

b) a+b-c+a-b+c-a-c+a-a+b+c

=.....................................

\(a,A=\left(2a+b+3c\right)-\left(a-b+c\right)\)

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

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

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

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

\(=4a+b+2c\)

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

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

\(=4a-2b+2c\)

Bài 1:

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

    A=-a+b+c+a+b+c

    A=(-a+a)+(b+b)-(c-c)

    A=0+2b-0

    A= 2b

b Thay b= -1 vào biểu thức A=2b ta có

A= 2.(-1)=-2

Bài 2: 

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)

A = 0 + 2b - 0

A = 2b 

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 = 2a + 0 - 0

B = 2a 

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

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

\(A=a+b-a+b+a-c-a-c\) 

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

\(A=0+2b+-2c\) 

\(A=2b-2c\) 

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

\(B=a+b-c+a-b+c-b-c+a-a+b+c\) 

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

\(B=2a+0+0\) 

\(B=2a\)

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