Đáp án:
\(x=3\)
Giải thích các bước giải:
\(\eqalign{
& \sqrt {{x^2} - 9} - \sqrt {x - 3} = 0 \cr
& DKXD:\,\,\left\{ \matrix{
{x^2} - 9 \ge 0 \hfill \cr
x - 3 \ge 0 \hfill \cr} \right. \Leftrightarrow \left\{ \matrix{
\left[ \matrix{
x \ge 3 \hfill \cr
x \le - 3 \hfill \cr} \right. \hfill \cr
x \ge 3 \hfill \cr} \right. \Leftrightarrow x \ge 3 \cr
& \Leftrightarrow \sqrt {{x^2} - 9} = \sqrt {x - 3} \cr
& \Leftrightarrow {x^2} - 9 = x - 3 \cr
& \Leftrightarrow {x^2} - x - 6 = 0 \Leftrightarrow \left[ \matrix{
x = 3\,\,\,\left( {tm} \right) \hfill \cr
x = - 2\,\,\left( {ktm} \right) \hfill \cr} \right. \cr
& Vay\,\,x = 3 \cr} \)