Question

How do you find the coordinates of the center of the circle `x^2 +y^2 -4x+ 6x =12`?

Answer 1

`r=7/2`

Explanation:

`x^2+y^2-4x+6x=12`
`x^2+y^2+2x-12=0`
`x^2+y^2+D x+E y+F=0`
`C(a,b) " center coordinates"`
`D=2" "E=0" "F=-12`
`a=-D/2=-2/2=-1`
`b=-E/2=0/2=0`
`r=1/2*sqrt(D^2+E^2-4*F)`
`r=1/2*sqrt((-1)^2+0+4*12)`
`r=1/2*sqrt(1+48)`
`r=1/2*sqrt 49`
`r=7/2`