Question

The equation of the circle whose center is at (2,1) and the radius is 3 is

Answer 1

$\bf \textit{equation of a circle}\\\\ (x- h)^2+(y- k)^2= r^2 \qquad center~~(\stackrel{2}{ h},\stackrel{1}{ k})\qquad \qquad radius=\stackrel{3}{ r} \\\\[-0.35em] \rule{34em}{0.25pt}\\\\ (x-2)^2+(y-1)^2=3^2\implies (x-2)^2+(y-1)^2=9$