Question

The equation of the director circle of the hyperbola $\frac{x^2}{36}-\frac{y^2}{16}=1$ is

• A. $x^2+y^2=20$
• B. $x^2+y^2=52$
• C. $(x-9{)}^2+(y-4{)}^2=0$
• D. $(x+9{)}^2+(y+4{)}^2=0$

Answer 1

Answer: (A)

$x^2+y^2=20$

for hyperbola, $\frac{x^2}{36}-\frac{y^2}{16}=1$

equation of director circle is $x^2+y^2=a^2-b^2=36-16=20$