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![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có:
a(b-c)-c(b-d)+a(c+d)+bc
=ab-ac-bc+cd+ac+ad+bc
=ab+cd+ad
Hok tốt !!!
a( b-c ) - c(b-d) + a(c+d) +bc
= ab -ac - bc + cd + ac + ad + bc
=ab + cd + ad
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a)= a-c+d-c+a-d
=2a-2c=2(a-c)
b)=-a-b+c-d+a-b-c-d
=-2b-2d
=2.(-b)-2d=2(-b-d)
c)=ab-ac-ad-ab-ac+ad
=-2.ac
![](https://rs.olm.vn/images/avt/0.png?1311)
D=(10-a+b)-(10-b+c)-(10-c-a)
D= 10-a+b-10+b-c-10+c+a
D=(10-10-10)-(a-a)+(b+b)-(c-c)
D= -10+2b
![](https://rs.olm.vn/images/avt/0.png?1311)
A=a(2b-c)-b(a+c)-(c+b)
=2ab-ac-ab-bc-c-b
=(2ab-ab)-ac-bc-c-d
=ab-ac-bc-c-b
B=(a+3b)(c-d)-(3a-d)(b+c)-2c(b-a)+2b(a+d)
=a.(c-d)+3b.(c-d)-3a.(b+c)+d.(b+c)-2bc+2ac+2ab+2bd
=ac-ad+3bc-3bd-3ab-3ac+bd+cd-2bc+2ac+2ab+2bd
=(-3ab+2ab)+(3bc-2bc)+(ac-3ac+2ac)-ad+(-3bd+bd+2bd)+cd
=-ab+bc-ad+cd
![](https://rs.olm.vn/images/avt/0.png?1311)
A = (-a - b + c) - (-a - b - c)
= -a - b + c + a + b + c
= (a - a) + (b - b) + (c + c)
= 0 + 0 + 2c
= 2c
A = (-a - b + c ) - ( -a - b - c )
A = -a -b - c + a + b + c
A = (-a + a ) + (-b + b ) + (c + c)
A= 0 + 0 + 2c
A= 2c
Vay A= 2c
tik nha
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có A=(-a-b+c)-(-a-b-c)
=-a-b+c+a+b+c
=(-a+a)+(-b+b)+(-c+c)
=0
Khi a=1 ; b=-1;c=2
Thì A =(-1+1+2)-(-1+1-2)
=2-2
=0
Ta có
+> 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
= 2(b-c)
+> B = (a+b-c) + (a-b+c) - (b+c-a) - (a-b-c)
= a+b-c+a-b+c-b-b+a-a+b+c
= (a+a+a-a) + (b-b-b-b+b) + (-c+c+c)
= 2a - b + c