# Why is my standard equation incorrect?

• August 23rd 2009, 02:17 AM
bobbyboy1111
Why is my standard equation incorrect?
What is the standard equation of the circle whose center is (-5,-4) and whose radius is 3?

(x + 5)^2 + (y + 4) = 9
• August 23rd 2009, 02:27 AM
running-gag
Quote:

Originally Posted by bobbyboy1111
What is the standard equation of the circle whose center is (-5,-4) and whose radius is 3?

(x + 5)^2 + (y + 4) = 9

It is actually $(x + 5)^2 + (y + 4)^2 = 9$

The vector linking the center C (-5,-4) to any point M(x,y) has coordinates (x-(-5),y-(-4)) or (x+5,y+4)

The distance between M and C is $\sqrt{(x + 5)^2 + (y + 4)^2}$