Question

Cho A = a + b - 5 ; B = - b - c + 1 ; C = b - c - 4 ; D = b - a

Chứng minh A + B = C - D

Answer 1

A=a+b-5

B=-b-c+1

C=b-c-4

D=b-a

A+B=a+b-5+(-b-c+1)

A+B=a+b-5-b-c+1

A+B=(b-b)+a-c-(5+1)

A+B=0+a-c-4

A+B=a-c-4

C-D=b-c-4-(b-a)

C-D=b-c-4-b+a

C-D=(b-b)+a-c-4

C-D=0+a-c-4

C-D=a-c-4

Vì a-c-4=a-c-4 nên A+B=C-D

Vậy A+B=C-D=a-c-4

Answer 2

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