Question

Write the equation of the circle that has a diameter of 8 and a center at (-1, 9).

Answer 1

(x + 1)² + (y - 9 )² = 43

Explanation:

got it right on my test!

Answer 2

(x + 1)² + (y - 9)² = 4²

Explanation:

equation of circle is (x - a)² + (y - b)² = r²

where a is x-coordinate of centre of circle, b is y-coordinate of centre of circle, r is the radius. radius = half of diameter.

(x - -1)² + (y - 9)² = 4²

(x + 1)² + (y - 9)² = 4²