Question 39797: Write an equation of the circle whose center is at the origin and the point (3,-6) is on the circle.
I know the the formula to use is this:
(x-h)squared + (y-k)squared = r squared Found 2 solutions by Nate, fractalier:Answer by Nate(3500) (Show Source):
You can put this solution on YOUR website! Yes the equatin is correct. But the point (h, k) is the center of the circle. Here that is (0. 0).
But since the point (3, -6) lies on the circle, its distance from the origin is the radius of the circle.
Its distance is found by
d^2 = 3^2 + (-6)^2
d^2 = 9 + 36
d^2 = 45
and since d^2 is really r^2, we have
x^2 + y^2 = 45