Find the equation of the circle that satisfies the given conditions.

Question

Center at the origin and passes through (7, 9)

130 = ?

Answer 1

any circle with centre at the origin has equation
x^2 + y^2 = r^2
simply sub in the point(7,9) to find the value of r^2

Answer 2

A circle is centered at the point (5, -4) and passes through the point (-3, 2).