[(A – B)2 + (B – C)2 + (C – A)2] = A B B C C A       1 A

2 . - DAP AN DE THI GVG TINH BAC NINH NAM 12 13
Toán DAP AN DE THI GVG TINH BAC NINH NAM 12 13

2

.(a + b + c).[(a – b)

2

+ (b – c)

2

+ (c – a)

2

] =

a b

b c

c a

 

 

1

a

. 1

b

. 1

c

.

.

 

 

b

c

a

 

 

=

 

 