(x^2)/25 - (y^2)/(b^2)=1
Find the directrices, foci, and eccentricity of hyperobola????
It would be much easier for us to help you if you have shown some work, because this question is quite straight forward.
Your equation describes a family of hyperbolae with the properties:
$\displaystyle e^2 = a^2+b^2~\implies~e^2=25+b^2$
Thus the foci have the coordinates:
$\displaystyle F_1\left(-\sqrt{25+b^2}, 0 \right) ; F_2\left(\sqrt{25+b^2}, 0 \right)$
The numerical eccenticity is $\displaystyle \epsilon = \frac ea$
and therefore the equation of the directrice is $\displaystyle D: x = \epsilon$
Since $\displaystyle b > 0 ~\implies~\epsilon > 1$