Question

Write the standard equation of a circle with a center (2,-8) and radius 9

Answer 1

The standard equation of a circle:

$(x-h)^2+(y-k)^2=r^2$

(h, k) - center

r - radius

We have:

(2, -8) → h = 2, k = -8

r = 9

Substitute:

$(x-2)^2+(y-(-8))^2=9^2\\\\(x-2)^2+(y+8)^2=81$