Question

Find centre and radius of the following circles

x² + y² – x + 2y – 3 = 0

Answer 1

2g = – 1

2f = 2

c = – 3

g = `(-1)/2` f = 1

Centre (– g, – f) = `(1/2, -1)`

Radius = `sqrt(g^2 + f^2 - "c")`

= `sqrt(1/4 + 1 + 3)`

`sqrt(1 + 4 + 12/4)`

`sqrt(17/4) = sqrt(17)/2`