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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
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rút gọn biểu thức
a,A=(a-b)-(a-b+c)
b,B=-(a+b+c)-(a+b-5)
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\(\text{-(a+b)-(b-c)-(a+c) }\)
\(-a-b-b+c-a-c\)
\(=-2a-2b\)
Đó là câu 1
Học tốt
\(-\left(a+b\right)-\left(b-c\right)-\left(a+c\right)=-a+b-b+c-a-c\)
\(=-2a\)
2\(-\left(-2a+b\right)+\left(b-c\right)-\left(-c+a\right)\)
\(=2a-b+b-c+c-a\)
\(=a\)
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a)A = (a - b) – (a – b + c)
A=a-b-a+b-c
A=(a-a)+(b-b)-c
A=-c
b)B = (a + b + c) – (a + b - 5)
B=a+b+c-a-b+5
B=(a-a)+(b-b)+(c+5)
B=c+5
a) A = (a - b) - (a - b + c)
A = a - b - a + b - c
A = -c
b) B = (a + b + c) - (a + b - 5)
= a + b + c - a - b + 5
= c + 5
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a) A=a+b-a+b+a-c-a-c
A=(a+b-a+b)+(a-a)-c-c
A=-2c
b)B=a+b-c+a-b-c-b-c+a-a+b+c
B=2a-2c-b
bài b hơi dài nên có thể mình bị sai
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a) - ( - a + c – d ) – ( c – a + d )
= a - c - d - c + a + d
= (a + a) + (-c - c) + (-d + d)
= 2a - 2c
b) – ( a + b - c + d ) + ( a – b – c –d )
= - a - b + c - d + a - b - c - d
= (-a + a) + (-b - b) + (c - c) + (-d - d)
= -2b - 2d
a) - ( - a + c - d) - ( c - a + d )
= a - c + d - c + a - d
= 2a
b) - ( a+ b - c + d ) + ( a -b -c -d )
= - a-b+c-d+a-b-c-d
=-2d -2b
c) a(b-c-d) - a(b+c-d)
= a(b-c-d-b-c+d)
= ab-ac-ad-ab-ac+ad
= -2ab-2ac
d) (a+b)(c+d)-(a+d)(b+c)
= ac+ad+bc+bd - (ab+ac+bd+cd)
= ac+ad+bc+bd-ab-ac-bd-cd
=ad+bc-ab-cd
![](https://rs.olm.vn/images/avt/0.png?1311)
1) \(=ac+ad+bc+bd-ab-ac-db-dc=ad+bc-dc-ab=d\left(a-c\right)-b\left(a-c\right)=\left(a-c\right)\left(d-b\right)\)
2) \(=ac-ad+bc-bd-ac-ad+bc+bd=2bc-2ad=2\left(bc-ad\right)\)
3) \(\left(a+b\right)\left(a+b\right)-\left(a-b\right)\left(a-b\right)=a^2+2ab+b^2-a^2+2ab-b^2=4ab\)
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\(\text{ -(a-b)+(-b+c)-(a+c)=-a+b-b+c-a-c=(-a-a)+(b-b)+(c-c)=-2a}\)
Đề bài:Phá ngoặc rồi rút gọn biểu thức
-(a-b)+(-b+c)-(a+c)
= - a + b - b + c - a - c
= -2a
Study well