Question

What is the equation of a circle whose center is at the origin and whose radius is 9?

x^2 + y^2 = 3


x^2 + y^2 = 9
x^2 + y^2 = 81

Answer 1

3, i hope this is helpful!

Answer 2

Hi there!

Points on circle are equidistant from its center.
This is th' distance called the radius of the circle.

• Cartesian form:-

r : √x² + y² = 9

r : x² + y² = 9²

r : x² + y² = 81

Hence,
Option 3ʳᵈ : x² + y² = 81 is Correct.

~ Hope it helps!