Question

Which of the following is the equation of a circle whose center is at the origin and whose radius is 4?
x2+ y2= 2
x2+ y2= 4
x2+ y2= 16

Answer 1

equation of circle wid radius \(r\) :

\(x^2 + y^2 = r^2\)

Answer 2

formula for a circle with center at \((h,k)\) and radius \(r\) is \[(x-h)^2+(y-k)^2=r^2\]
Your center is the origin \((0,0)\) so it reduces to @ganeshie8's form