Question

Bài 16 Chứng minh rằng

(a-b-c)+(-a+b-c)=-(a-b+c) thì a=b+c

Answer 1

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

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

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

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

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

\(\Rightarrow a=b+c\)

\(\RightarrowĐPCM\)

Answer 2

ta co : (a-b-c)+(-a+b-c)=-(a-b+c)

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

=> -2c+c=-a+b

=> -c=b-a

=> -c-b=-a

=> -(b+c)=-a

=> b+c=a ( dpcm)