Đáp án:
Giải thích các bước giải:
$\begin{array}{l}
\frac{x}{a} + \frac{y}{b} + \frac{z}{c} = 1\\
\Rightarrow {(\frac{x}{a} + \frac{y}{b} + \frac{z}{c})^2} = 1\\
\Leftrightarrow \frac{{{x^2}}}{{{a^2}}} + \frac{{{y^2}}}{{{b^2}}} + \frac{{{z^2}}}{{{c^2}}} + 2 \times \frac{{xyc + yza + xzb}}{{abc}} = 1\\
\\
\frac{a}{x} + \frac{b}{y} + \frac{c}{z} = 0 \Leftrightarrow \frac{{ayz + xzb + xyc}}{{xyz}} = 0 \Leftrightarrow ayz + xzb + xyc = 0\\
\Rightarrow \frac{{{x^2}}}{{{a^2}}} + \frac{{{y^2}}}{{{b^2}}} + \frac{{{z^2}}}{{{c^2}}} = 1
\end{array}$
