Given the equation of an hyperbola in the form:
[tex] \frac{(x-a)^2}{b^2}- \frac{(y-c)^2}{d^2}=1 [/tex]
Then the focus of the hyperbola is [tex](\pm\sqrt {b^2+d^2},0)[/tex]
Compute like this:
[tex]\sqrt{81+144}=15[/tex]
So the two focus points are [tex](\pm15,0)[/tex]
The vertices are given by the formula: [tex](\pm a,0)[/tex]
We deduce the two vertices of the given hyperbola: [tex](\pm9,0)[/tex]
since [tex] \sqrt{81}=9 [/tex]
