Question

Find the radius of the circle whose equation is (x - 2)² + (y - 4)² = 9.

Answer 1

`\bf \textit{equation of a circle}\\\\ (x- h)^2+(y- k)^2= r^2 \qquad center~~(\stackrel{}{ h},\stackrel{}{ k})\qquad \qquad radius=\stackrel{}{ r}\\\\ -------------------------------\\\\ (x- \stackrel{h}{2})^2+(y- \stackrel{k}{4})^2= 9\implies (x- \stackrel{h}{2})^2+(y- \stackrel{k}{4})^2= \stackrel{r}{3^2} ~~ \begin{cases} center~(2,4)\\ radius=3 \end{cases}`