Question

Determine o centro e o raio de cada circunferência descrita. X2 + y2 + 4x – 2y + 1 = 0.

Answer 1

$\large\boxed{\begin{array}{l}\sf x^2+y^2+4x-2y+1=0\\\sf x^2+4x+4+y^2-2y+1=-\diagdown\!\!\!1+4+\diagdown\!\!\!1\\\sf (x+2)^2+(y-1)^2=4\\\sf -a=2\implies a=-2\\\sf -b=-1\implies b=1\\\sf r^2=4\\\sf r=\sqrt{4}\\\sf r=2\\\sf C(-2,1)~~r=2\end{array}}$