Question

Write the equation of the circle: Center at P(2 , -1) and a diameter of 10m

Answer 1

An equation of the circle is
(x-h)² +(y-k)² =r²,
where (h,k) are coordinates of the center of the circle, and r is a radius of the circle.
We have h=2, k= -1, and radius r=diameter/2=10/2=5.

The equation of our circle is 
(x-2)²+(y+1)²=25