A circle is centered at (−4, −6) and has a radius of 3. Which of the following is the equation for this circle?

(x + 4)2 + (y + 6)2 = 3

(x − 4)2 + (y − 6)2 = 9

(x − 4)2 + (y − 6)2 = 3

(x + 4)2 + (y + 6)2 = 9

Question

A circle is centered at (−4, −6) and has a radius of 3. Which of the following is the equation for this circle?

 (x + 4)2 + (y + 6)2 = 3

 (x − 4)2 + (y − 6)2 = 9

 (x − 4)2 + (y − 6)2 = 3

 (x + 4)2 + (y + 6)2 = 9

christina166 · Answer

@pooja195 May you please help.

jagr2713 · Answer

What do we do first?

marcelie · Answer

hmm.. you can plugin the points onto ur equation

marcelie · Answer

http://www.whsad.org/wp-content/uploads/2015/01/circleEquation.png

christina166 · Answer

I really don't get it :/

bobo-i-bo · Answer

Hmmm, do you understand/know the equation for a circle of radius one, centered at the point (0,0)?

christina166 · Answer

Not really, I'm sorry I feel stupid.

mathmale · Answer

Most basic equation of a circle is the one centered at the origin, (0,0):$$x^2 + y^2 = r^2$$

mathmale · Answer

If, on the other hand, your circle is centered at (h,k), the basic equation for that circle of radius r is$$(x-h)^2+(y-k)^2=r^2$$

christina166 · Answer

Oh okay.

mathmale · Answer

Now you're given the coordinates of the center of the circle.  They are (-4,-6), and the radius is 3.

mathmale · Answer

Substitude -4 for x, -6 for k and 3 for r into the most recent equation I gave you.

christina166 · Answer

Oh, thank you!

mathmale · Answer

Next time you feel stuck on a problem like this one, look up the formula(s) on the 'Net.
I would have looked up "equation of a circle."  try it.  What a great tool the 'Net can be!
You're very welcome, Christina.  See you again.

christina166 · Answer

Okay, is it okay if you help me with the last question I was stuck with? @mathmale

mathmale · Answer

Sure.  Please post it here.