CHO A3+ + = B3 C3 3 ABC A B C , ( , ,  0 ) , TÍNH P 1 A 1 B 1 CB C AH...

Bài 25: Cho ^a

^{+ + = b}

^c

^{3 abc a b c ,} ( ^{, ,  0} ) ^{, Tính P 1 a 1 b 1 c}

b c a

HD :

Ta có : ^a

^{+ + b}

^c

⁼ ( ^{a b c + +} ) ( ^a

^{+ b}

^{+ − c}

^{ab bc ca − −} ) ^{+ 3 abc , Mà a}

^{+ + b}

^c

^{= 3 abc Nên}

+ + + − − −

+ + = = = = = −

TH1 : 0 a b b c a . . c c . a . b 1

a b c P

b c a b c a

TH2 : a

+ + − b

c

ab bc ca − − = = = = = = + ⁰ a b c P ( )( )( ) 1 1 1 1 1 1 + + = 8

+ + +

   

= +     +   +  

= = , Tính 1 a 1 b 1 c

B b c a