Question

giúp mình nha

Answer 1

Có a+b+c=0

<=> a+b=-c

<=>(a+b)^3=-c^3

<=>a^3+3a^2b+3ab^2+b^3=-c^3

<=>a^3+b^3+c^3=-3ab(a+b)

<=>a^3+b^3+c^3=-3ab(-c)=3abc

\(A=\dfrac{a^2}{bc}+\dfrac{b^2}{ac}+\dfrac{c^2}{ab}=\dfrac{a^3}{abc}+\dfrac{b^3}{abc}+\dfrac{c^3}{abc}=\dfrac{a^3+b^3+c^3}{abc}=\dfrac{3abc}{abc}=3\)