Question

A circle is centered at (5, −9) and has a radius of 12. Which of the following is the equation for this circle?

(x − 5)2 + (y + 9)2 = 12
(x − 5)2 + (y + 9)2 = 144
(x + 5)2 + (y − 9)2 = 144
(x + 5)2 + (y − 9)2 = 12

Answer 1

well, the equation for a circle is \[ ( x - h )^2 + ( y - k )^2 = r^2 \]

where h and k are the centre

Answer 2

so we are given

r=12
h=5
k=-9

just plug the numbers in