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![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=\left(a+b\right)-\left(a-b\right)+\left(a-c\right)-\left(a+c\right)\)
\(\Leftrightarrow A=a+b-a+b+a-c-a-c\)
\(\Leftrightarrow A=\left(a-a+a-a\right)+\left(b+b\right)-\left(c+c\right)\)
\(\Leftrightarrow A=0+2b-2c\)
\(\Leftrightarrow A=2b-2c\)
\(\Leftrightarrow A=2\left(b-c\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bỏ dấu ngoặc rồi thu gọn biểu thức sau:
a) (a+b)-(a-b)+(a-c)-(a+c)
=a+b-a+b+a-c-a-c
=2b-2c
=2(b-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
=3a+3b-3b
=3(a+b-c)
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)
=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
=(a+a+a-a)+(b-b-b+b)+(-c+c-c+c)
=2a
![](https://rs.olm.vn/images/avt/0.png?1311)
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!
![](https://rs.olm.vn/images/avt/0.png?1311)
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
![](https://rs.olm.vn/images/avt/0.png?1311)
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`
\(A=\left(a+b\right)-\left(a-b\right)+\left(a-c\right)-\left(a+c\right)\)
\(A=a+b-a+b+a-c-a-c\)
\(A=2b-2c\)
\(B=\left(a+b-c\right)+\left(a-b+c\right)-\left(b+c-a\right)-\left(a-b-c\right)\)
\(B=a+b-c+a-b+c-b-c+a-a+b+c\)
\(B=2a\)
![](https://rs.olm.vn/images/avt/0.png?1311)
$A = (a + b) - (a + b) + (a - c) - (a + c)$
$A=a+b-a-b+a-c-a-c$
$A=-2c$
A = (a + b) - (a - b) + (a - c) - (a + c)
A = a + b - a + b + a - c - a - c
A = 2b