Toán Lớp 9: Tìm x $\sqrt{x – 3}$ – 2$\sqrt{x^{2} – 9}$ = 0
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Toán Lớp 9: Tìm x $\sqrt{x – 3}$ – 2$\sqrt{x^{2} – 9}$ = 0
Comments ( 2 )
$\sqrt{x-3}$ – 2$\sqrt{x^{2}-9}$ = 0
<=> $\sqrt{x-3}$ – 2$\sqrt{(x-3)(x+3)}$ = 0
<=> $\sqrt{x-3}$(1 – 2$\sqrt{x+3}$) = 0
\(\left[ \begin{array}{l}\sqrt{x-3} = 0\\1 – 2\sqrt{x+3} = 0\end{array} \right.\)
<=> \(\left[ \begin{array}{l}x-3 = 0\\2\sqrt{x+3} = -1\end{array} \right.\)
=> x = 3 (vì 2$\sqrt{x+3}$ $\geq$ 0 => vô lí)