rút gọn :
( a + b ) . ( c - d ) - ( a - b ) . ( c + d )
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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
a(b-c-d)-a(b+c-d)=a(b-c-d-b+c-d)=a[(b-b)-(c-c)-(d+d)]=2[0-2d]=2*(-2d)=2(1+d)
(a+b+c+d).((a+b-c-d)= ((a+b)+(c+d)).((a+b)-(c+d))=(a+b)2-(a+b)2=0
- (a + b - c) + (b - c + d) - (-a + b + d)
= -a -b + c + b - c + d + a - b - d
= -b
\(A=\left(a-b-c-d\right)+\left(b-c+d-a\right)\)
\(=a-b-c-d+b-c+d-a\)
\(=-2c\)
-(a+b-c+d)+(a-b-c-d)=-a-b+c-d+a-b-c-d=(-a+a)-(b+b)+(c-c)-(d+d)=0-2b+0-2d=-2b+(-2)d=-2(b+d)
-(a+b-c+d)+(a-b-c-d)
= -a-b+c-d+a-b-c-d
= -2b-2d
Nhấn đúng cho mk nha!!!!!!!!!!!
(a+b).(c+d)-(a+d).(b+c)
=ac+ad+bc+bd-ab-ac-bd-dc
=(ac-ac)+(bd-bd)+(ad-ab)+(bc-dc)
=0+0+a.(d-b)+c.(b-d)
=a.(d-b)+c.(b-d)
Hok tốt
\(\left(a+b\right)\left(c-d\right)-\left(a-b\right)\left(c+d\right)\)
\(=\left(ac-ab+bc-bd\right)-\left(ac+ad-bc-bd\right)\)
\(=ac-ad+bc-bd-ac-ad+bc+bd\)
\(=2bc-2ad\)
\(=2\left(bc-ad\right)\)