cần gấp nha m.n

I

iu278

Ta có:a+b+c=0 (a+b+c)^2=0
Hay: a^2+b^2+c^2+2ab+2ac+2bc=0
1+2(ab+ac+bc)=o
ab+bc+ac=1/2
(ab+bc+ac)^2=1/4
a^2b^2+a^2c^2+b^2c^2+2abc(a+b+c)=1/4
a^2b^2+a^2c^2+b^2c^2=1/4
Ta lại có: a^2+b^2+c^2=1 (a^2+b^2+c^2)^2=1
Hay:a^4+b^4+c^4+2a^2b^2+2b^2c^2+a^2c^2=1
a^4+b^4+c^4+2(a^2b^2+b^2c^2+a^2c^2)
a^4+b^4+c^4+1/2=1
a^4+b^4+c^4= 1/2
 
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