CHO A+B+C = 0A B B C C A C A B      C A B A B B C C A  CMR

câu 1: - DE THI HSG TOAN LOP 8 CO DAP AN
DE THI HSG TOAN LOP 8 CO DAP AN

Câu 1:

Cho a+b+c = 0

a b b c c a c a b

  

    

c a b a b b c c a

CMR: ( )( ) 9