Answer
(a) center $(h,k)=(-2,-1)$ and radius $r=5$.
(b) See graph.
(c) $(-2\pm2\sqrt 6,0)$, $(0,-1\pm\sqrt {21})$.
Work Step by Step
(a) Given $x^2+y^2+4x+2y-20=0\longrightarrow (x+2)^2+(y+1)^2=25$, we can find the center $(h,k)=(-2,-1)$ and radius $r=5$.
(b) See graph.
(c) We can find the x-intercept(s) (let y=0) $(-2\pm2\sqrt 6,0)$, y-intercept(s) (let x=0) $(0,-1\pm\sqrt {21})$.
