Question

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

Answer 1

The equation of a circle is:\[\Large (x-h)^2+(y-k)^2=r^2\]

And we were given:\[\Large (h,\;k)\quad=\quad (2.5,\;-3.5)\]And,\[\Large d\quad=\quad 12\]

Answer 2

So the equation of the circle involves the `radius`.
Do you understand how to write our `diameter` in terms of the `radius`?

Answer 3

http://www.mathwarehouse.com/geometry/circle/images/equation-of-circle/general-formula-equation-of-circle.png