ข้อ6
ให้ $\sqrt{\frac{x}{1-x}} = a$
จะได้ $ a + \frac{1}{a} = \frac{13}{6}$
$a = \frac{2}{3} , \frac{3}{2}$
$\sqrt{\frac{x}{1-x}} = \frac{2}{3} , \sqrt{\frac{x}{1-x}} = \frac{3}{2}$
$ x = \frac{4}{13} , \frac{9}{13}$
$ \frac{4}{13} + \frac{9}{13} = 1 $
$\therefore a+b = 1$
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