Question 819369
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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
{{{a^2+b^2=16}}}     |Note use or ^  (uppercase 6)
this is an equation of a Circle having C(0,0) and r = 4