Question

What is the equation of the circle with center (0, 0) that passes through the point (–4, –6)?

Answer 1

If the center is in point P(a,b) and has a radius r then circle equation is:

(x-a)²+(y-b)²=r².

In your task we've got P(0,0) so the circle equation is x²+y²=r².

We have to find r. Radius start at (0,0) and end at (-4,-6) therefore

r=√((-4)²+(-6)²) and

r²=(-4)²+(-6)²=16+36=52.

So answer is x²+y²=52.