[tex] {x }^{2} + {y}^{2} + 4x - 2y = - 1 \\ the \: equation \: of \: a \: circle \: in \: \\ the \: xy \: plane \\ is \: shown \: \\ above \\ \\what \: is \: the \: radius \: of \: the \\ circle \\ a 2 \\ b3 \\ c4 \\ d9[/tex]
a 2
b 3
c 4
d 9
​