Which of the following circle equations represents a circle whose center is at (0, 0)?Select one of the options below as your answer: A. x2 + y2 = 45 B. (x − 3)2 + (y − 5)2 = 0 C. (x + 3)2 + (y − 3)2 = 0 D. x2 + (y − 1)2 = 1

Question

whpalmer4 · Answer

Use the formula I gave you on the last problem.  Once again, the formula for a circle with radius $r$ and center at $(h,k)$ is$$(x-h)^2+(y-k)^2=r^2$$

Your center is at $(0,0)$ so $h=0$ and $k=0$.  Substitute those values, simplify the equation and compare with the answer choices.

anonymous · Answer

so its c?

whpalmer4 · Answer

Okay, let's do what I just suggested and rewrite the formula with $h=0$ and $k=0$:

$$(x-0)^2+(y-0)^2=r^2$$$$x^2+y^2=r^2$$

Here are the answer choices:
A: $x^2+y^2=45$
B: $(x − 3)^2 + (y − 5)^2 = 0$
C. $(x + 3)^2 + (y − 3)^2 = 0$
D. $x^2 + (y − 1)^2 = 1$

Which of those choices most resembles $x^2+y^2=r^2$?

anonymous · Answer

ohhhhh A

whpalmer4 · Answer

Yes! :-)

anonymous · Answer

yay thanks :D Im stressin i have 20 minutes left and 7 more questions

whpalmer4 · Answer

hopefully you've just figured out how to do them :-)

anonymous · Answer

thanks