How do you find the center and radius of the circle (x - 3) ^2 + (y + 1) ^2 = 9(x−3)2+(y+1)2=9?

1 Answer
radee
Feb 5, 2016

Center (3, -1)(3,−1)
radius = 3radius=3

Explanation:

The centre-radius form of a circle is (x - h)^2 + (y - k)^2 = r^2(x−h)2+(y−k)2=r2 with the centre being (h, k)(h,k) and rr as the radius.

Given this, we would know that the center of the circle is (3,-1)(3,−1) and the radius is 3.

Luckily we are given the centre-radius form so we can easily get/compute for what was asked. However, if we are given the standard form of a circle, we should first do completing the square to transform it into its center-radius form.

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