Toan 8

H

hiendang241

ta có ($\frac{x}{a}$ +$\frac{y}{b}$ +$\frac{z}{c}$)^2=1
\Rightarrow $\frac{x^2}{a^2}$ +$\frac{y^2}{b^2}$ +$\frac{z^2}{c^2}$ +2($\frac{cxy+ayz+xbz}{abc}$)=1 (1)
mà $\frac{a}{x}$+$\frac{b}{y}$+$\frac{c}{z}$=0
nen\Rightarrow ayz+bxz+cxy=0(2)
1,2\Rightarrow $\frac{x^2}{a^2}$ +$\frac{y^2}{b^2}$ +$\frac{z^2}{c^2}$=1
 
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