Question

A circle has its center at (-1, 2) and a radius of 3 units. What is the equation of the circle?

(x - 1)2 + (y + 2)2 = 3

(x + 1)2 + (y - 2)2 = 3

(x + 1)2 + (y + 2)2 = 9

(x + 1)2 + (y - 2)2 = 9

Answer 1

hint:

i'll give you a demo

a circle has center (-3, 4) and radius 2

equation of circle is \[(x-h)^2 + (y-k)^2 = r^2\]
where (h,k) is the center and r is the radius

since in my example h is -3 and k is 4 i will have
\[(x- - 3)^2 + (y-4)^2 = 2^2\]
\[\implies (x +3)^2 + (y-4)^2 = 4\]
do you get the idea?

Answer 2

Standard equation is given by:

\[\large (x-h)^2 + (y-k)^2 = r^2\]

h. k are the centre and r is the radius and try to find it..

Answer 3

idk

Answer 4

what is the coordinate of your center in this problem?

Answer 5

i think its D ?

Answer 6

Yes...

Answer 7

thanks....

Answer 8

But how ???

Answer 9

i followed your example

Answer 10

\[(x- -1)^2 + (y-3) = 3^2\]
\[\implies (x+1)^2 + (y-3) = 9 \checkmark\] you're right

Answer 11

thanks(: