Find the equation of the hyperbola satisfying the give conditions: Foci $(\pm 3 \sqrt{5}, 0)$, the latus rectum is of length $8 .$
Foci $(\pm 3 \sqrt{5}, 0)$, the latus rectum is of length 8 .
Here, the foci are on theĀ x-axis.
Therefore, the equation of the hyperbola is of the form $\frac{x^{2}}{a^{2}}-\frac{y^{2}}{b^{2}}=1$.
Since the foci are $(\pm 3 \sqrt{5}, 0), c=\pm 3 \sqrt{5}$.
Length of latus rectum $=8$
$\Rightarrow \frac{2 b^{2}}{a}=8$
$\Rightarrow b^{2}=4 a$
We know that $a^{2}+b^{2}=c^{2}$.
$\therefore a^{2}+4 a=45$
$\Rightarrow a^{2}+4 a-45=0$
$\Rightarrow a^{2}+9 a-5 a-45=0$
$\Rightarrow(a+9)(a-5)=0$
$\Rightarrow a=-9,5$
Since $a$ is non-negative, $a=5$.
$\therefore b^{2}=4 a=4 \times 5=20$
Thus, the equation of the hyperbola is $\frac{x^{2}}{25}-\frac{y^{2}}{20}=1$.