Question

The directrix of the hyperbola $\frac{x^{2}}{9} - \frac{y^{2}}{4}$ = 1 is

• A. x = $\frac{9}{\sqrt{13}}$
• B. y = $\frac{9}{\sqrt{13}}$
• C. x = $\frac{6}{\sqrt{13}}$
• D. y = $\frac{6}{\sqrt{13}}$

Answer 1

Answer: (A)

x = $\frac{9}{\sqrt{13}}$

Answer 2

Equation of directrix

Ž x = ± $\frac{a}{e}$

$\frac{x^{2}}{9} - \frac{y^{2}}{4}$ = 1 Ž $\left\{ \begin{matrix} a^{2} = 9 \\ b^{2} = 4 \end{matrix} \right.\$

& e = $\sqrt{1 + \frac{b^{2}}{a^{2}}} = \frac{\sqrt{13}}{3}$