Circle P has a radius of 8 units with center P at (-2, 1). Which equation defines circle P?

Question

anonymous · Answer

A. (x + 2)2 + (y – 1)2 = 8

 B. (x – 2)2 + (y + 1)2 = 8

C.  (x + 2)2 + (y – 1)2 = 64

D.  (x – 2)2 + (y + 1)2 = 64

anonymous · Answer

the equation of a circle with center (a,b) and radius r is:
(x-a)^2 + (y-b)^2 = r^2

anonymous · Answer

I'm really confused and I don't know how to use the formula. Could you explain?

agent47 · Answer

(x-(-2))^2+(y-1)^2=8^2

agent47 · Answer

That's what he/she means.

anonymous · Answer

$$(x-a)^{2}+(y-b)^{2}=r^{2}$$

anonymous · Answer

where (a,b) is the center of your circle and r is the radius

anonymous · Answer

In your case a=-2, b=1, and r = 8
put these into the general equation of a circle that I've given you

anonymous · Answer

How would I find x and y? I'm not good at equations like this "/

agent47 · Answer

You don't need x and y... you just need to see where in your equation are a, b, and r

agent47 · Answer

I don't even think you're trying  to understand what we're saying.. Come on, pay attention..

anonymous · Answer

okay, thanks. I get it now.

anonymous · Answer

It's not as hard as I thought

agent47 · Answer

An equation of a circle is:
(x-h)^2+(y-k)^2=r^2
Where (h;k) is the center and r is the radius.
Your center is (-2;1), radius is 8
Plug everything back into the equation of a circle to get the result.

anonymous · Answer

Thanks Agent47