Question

( a+b-c)+(a-b+c)-(b+c-a)-(a-b-c)

Answer 1

(a+b-c)+(a+b+c)-(b+c-a)-(a-b-c)

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

=2a+2b

=2(a+b)

Answer 2

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Answer 3

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

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

A=0+0+2*c

A=2*c

Answer 4

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

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

=0+0+3c-d

=3c-d