Question

1. If a circle is centered at (5, -7) and goes through the point (-3, -1), what is the radius?

2. Why do we prefer the standard form for the equation of a circle over the general form?

Answer 1

Answer: r = 11.3

Explanation:

Standard form : (x-h)2 + (y-k)2 = r2

(h,k) = (5,7)

(x,y) = (-3,-1)

r2 = (-3-5)2 + (-1-7)2

r2 =
`-8^(2) + -8^(2) = 64 + 64 = 128\\r = √(128) = 11.3`

When coordinates of the center of the circle and a point on the circle are known, Standard form is the one to use.