Equation of a circle question?

Question

Write the equation of a circle with a center at (2.5, –3.5) and a diameter of 12.
Answer

(x + 2.5)2 + (y – 3.5)2 = 12

(x – 2.5)2 + (y + 3.5)2 = 36

(x + 2.5)2 + (y – 3.5)2 = 36

(x – 2.5)2 + (y + 3.5)2 = 144

Answer 1

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

Where (h , k) is center of circle and r is radius.

The centre of circle (h, k) = (2.5, - 3.5)

And the diameter = 12

Radius r = d/2

r = 12/2

r = 6

Substitute r = 6 and (h , k) = (2.5, - 3.5) in Standard form.

(x - 2.5)² + (y - (- 3.5) ]² = 6²

The circle equation is (x - 2.5)² + (y + 3.5)² = 36.

Second option is correct.