Question

How do you write the equation for a circle with center (-4, 2) and passing through (0, 5)?

Answer 1

`x^2+y^2+8x-4y-5=0`

Explanation:

the ray is the distance between center and point

`r^2=(0+4)^2+(5-2)^2`
`r^2=16+9`
`r^2=25`

so the requested equation is obtained by:

`(x+4)^2+(y-2)^2=25`
`x^2+8x+16+y^2-4y+4-25=0`
`x^2+y^2+8x-4y-5=0`