(a+b) . (c+d) - (a+d). (b+c)

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

=ac+bc+ad+bd-ab-db-ac-dc

=(ac-ac)+(bd-db)+bc+ad-ab-dc

=0+0+bc+ad-ab-dc

=bc+ad-ab-dc

=(ad-ab)-(dc-bc)

=a(d-b)-c(d-b)

=(d-b).(a-c)

nhớ ủng hộ cho mình 1 đúng nhe

a, -( -a + c - d) - ( c - d + d) =  a - c + d - c + d - d =  a + d

b, - ( a+b-c+d) + (a-b-c-d) = -a -b+c-d + a-b-c-d = -2b + (-2c)= -2(b+c)

a: \(\left(a-b-c\right)-\left(-c+b+a\right)-\left(a-b\right)\)

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

\(=-a-b\)

b: \(a\left(b+c\right)-a\left(b+d\right)-\left(1+ac-ad\right)\)

\(=ab+ac-ab-ad-1-ac+ad\)

=-1

bạn xem ở câu hỏi tương tự

cau day có dung ko bn minh thay no cu sai sai sao í

a. (a+b).(a+b)

= a+b.a+b

= (a+b)²

b, (a-b).(a-b)

= a-b.a-b

= (a-b)² 

a,(a+b).(a+b)

=(a+b).a+(a+b).b

=a²+ba+ab+b²

=(a²+b²)+2ab

b,(a-b).(a-b)

=(a-b).a-(a-b).b

=a²-ba-ab-b²

=(a²-b²)-(ab-ba)

=a²-b²

a)(a+b)(a+b)=a(a+b)+b(a+b)=a²+ab+ab+b²=a²+2ab+b²

b)(a-b)(a-b)=a(a-b)-b(a-b)=a²-ab-ab+b²=a²-2ab+b²

1) -a(-a+c-d)-(c-a+d)

=ad-ac+a²-c+a-d

2) -(a+b)-(c+d)+(a-b-c-d)

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

=-2b-2c-2d

3) a(b-c-a)-a(b+c-d)

=-ac+ab-a²+ad-ac-ab

=ad-2ac-a²