Question 624450
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi,
Note:Standard Form of an Equation of a Circle is {{{(x-h)^2 + (y-k)^2 = r^2}}}  
where Pt(h,k) is the center and r is the radius
{{{ x^2+y^2 }}} =12    C(0,0)    {{{r = sqrt(12) = 2sqrt(3)}}} 
{{{drawing(300,300,   -6, 6, -6, 6,  grid(1),
circle(0, 0,sqrt(12)),
circle(0, 0,0.3),
graph( 300, 300, -6, 6, -6, 6))}}}