Question

Câu 1: Bỏ dấu rồi thu gọn biểu thức:

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

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

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Answer 1

\(A=\left(a+b\right)-\left(-a-b\right)+\left(a-c\right)-\left(a+c\right)\)

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

\(A=\left(a+a+a-a\right)+\left(b+b\right)+\left(-c-c\right)\)

\(A=3a+2b-2c\)

\(B=\left(a+b-c\right)+\left(a-b+c\right)-\left(b+c-a\right)-\left(a-b-c\right)\)

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

\(B=\left(a+a+a-a\right)+\left(b-b-b+b\right)+\left(-c+c-c+c\right)\)

\(B=3a\)

Answer 2

a) \(A=\left(a+b\right)-\left(-a-b\right)+\left(a-c\right)+\left(a+c\right)\)

\(=a+b+a+b+a-c-a-c=2a+2b-2c=2\left(a+b-c\right)\)

b) \(B=\left(a+b-c\right)+\left(a-b+c\right)-\left(b+c-a\right)-\left(a-b-c\right)\)

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

\(=3a\)

Answer 3

Bài của  Trần Nhật Quỳnh⁰⁷ bị sai câu a) rồi
a+a+a-a=3a-a=2a không phải =3a

Answer 4

@qad509 : à ờ ==' dạo này già rồi nên lú 

Answer 5

a, \(A=\left(a+b\right)-\left(-a-b\right)+\left(a-c\right)-\left(a+c\right)\)

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

\(=2a+2b-2c\)

b, \(B=\left(a+b-c\right)+\left(a-b+c\right)-\left(b+c-a\right)-\left(a-b-c\right)\)

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

\(=2a\)