Question

Write the equation of a circle that has center (2,-4) and passing through (4,-1)

Answer 1

r^2=(x-2)^2+(y-(-4))^2

hold on i'll find r

Answer 2

why is it not\[r^2=(x+4)^2+(y-2)^2\]?

Answer 3

Use distance formula to find r
sqrt((delta x)^2+(delta y)^2)

delta x just means difference in x which is xf-xi = 4-2

Same for delta y

Answer 4

oh no wait I remember...

Answer 5

the formula for a circle with center (h,k) is
r^2=(y-k)^2+(x-h)^2

Answer 6

more info

http://www.regentsprep.org/Regents/math/algtrig/ATC1/circlelesson.htm

Answer 7

there is no more info

Answer 8

yeah, but those links always confuse me
and then how do you find r again, isn't there some easy way?

Answer 9

Use distance formula to find r
sqrt((delta x)^2+(delta y)^2)

delta x just means difference in x which is xf-xi = 4-2

Same for delta y

Answer 10

well they tell you the center of the circle, so we know h and k

Answer 11

yes colorful you have it a little mixed around (x-h)^2+(y-k)^2=r^2

Answer 12

well whether you write
(x-h)^2+(y-k)^2=r^2
or
(y-k)^2+(x-h)^2=r^2
it's the same thing, isn't it?
and the picture should be something like this