If x + y + z = 0, then (x^2)/yz + (y^2)/zx + (z^2)/xy is equals to:

\(\frac{x^2}{yz}\) + \(\frac{y^2}{zx}\) + \(\frac{z^2}{xy}\)

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This shows similarity.

then put x = y = z

\(\frac{x^2}{x^2}\) + \(\frac{x^2}{x^2}\) + \(\frac{x^2}{x^2}\) = 3