Question

Find the equation of the circle with center at (-1, 3) and radius of 4. a. (x - 1)2 + (y + 3)2 - 4 c. (x - 1)2 + (y + 3)2 = 16 b. (x+1)+(-3)- 4 d. (x + 1)2 + (y - 3)2 - 16

Answer 1

$\textit{equation of a circle}\\\\ (x- h)^2+(y- k)^2= r^2 \qquad center~~(\stackrel{-1}{ h},\stackrel{3}{ k})\qquad \qquad radius=\stackrel{4}{ r} \\\\\\\ [x-(-1)]^2+[y-3]^2=4^2\implies (x+1)^2+(y-3)^2=16$