Which of the following is the equation of the circle with the center at the origin and r = 4?
(x + 1)2 + (y + 1)2 = 4

x2 + y2 = 4

(x - 1)2 + (y - 1)2 = 16

x2 + y2 = 16

Question

Which of the following is the equation of the circle with the center at the origin and r = 4? 
(x + 1)2 + (y + 1)2 = 4
		
x2 + y2 = 4
		
(x - 1)2 + (y - 1)2 = 16
		
x2 + y2 = 16

jdoe0001 · Answer

$\bf center \to origin\to ({\color{red}{ 0}},{\color{blue}{ 0}})\qquad radius=4
\ \quad \
(x-{\color{red}{ h}})^2+(y-{\color{blue}{ k}})^2=r^2$

what do you think?

anonymous · Answer

I think it's C.

jdoe0001 · Answer

well, why not just plug in the values, see what you get