Question

Write the equation in standard form for the circle with radius 3 centered at the origin

Answer 1

$\text{The equation in standard forn of the circle with radius r and a center}\\\text{in A(a; b) is}\ (x-a)^2+(y-b)^2=r^2\\\\\text{We have: r=3 and A(0; 0)}\\\\\text{substitute:}\\\\(x-0)^2+(y-0)^2=3^2\to\boxed{x^2+y^2=9}$