Question

Chứng tỏ :

1/ (a - b + c ) - ( a + c ) = -b

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

3 / - ( a + b - c ) + ( a - b - c ) = -2b

Còn nữa nha

Answer 1

\(1.\left(a-b+c\right)-\left(a+c\right)=-b\)

Ta có: \(a-b+c-a-c\)

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

\(=-b\left(ĐPCM\right)\) 

Answer 2

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

Ta có: \(a+b-b+a+c\)

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

\(=2a+c\left(ĐPCM\right)\)

Answer 3

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

=a-b+c-a-c

=-b (đổi vị trsi là ra)

=> đpcm

Lm hơi tắt, sr..

Answer 4

\(3.-\left(a+b-c\right)+\left(a-b-c\right)=-2b\)

Ta có: \(-a-b+c+a-b-c\)

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

\(=-2b\)

Answer 5

1/ Ta có : 

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

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

\(=-b\left(đpcm\right)\)

2/ Ta có :

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

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

\(=2a+c\left(đpcm\right)\)

3/ Ta có :

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

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

\(=-2b\left(đpcm\right)\) 

Answer 6

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

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

=\(2a+c\)

=> Đpcm

Answer 7

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

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

=-2b

=> Đpcm