Question

Equation of circle centered at extremity of positive minor axis and passing through the focus (on positive $x$-axis) of the ellipse $\frac{x^2}{16}+\frac{y^2}{9}=1$ is

• A. $x^2+y^2-6 y-7=0$
• B. $x^2+y^2-6 y=0$
• C. $x^2+y^2-6 y-16=0$
• D. $x^2+y^2-3 x-3 y=0$

Answer 1

Answer: (A)

Centre $\equiv(0,3) $ focus $S \equiv(\sqrt{7}, 0)$
radius $=B S=4$
$\therefore$ its equation is $x^2+(y-3)^2=4^2$