Question 73350
Using the formula:
{{{A=pi*r^2}}}plug in A=900
{{{900=pi*r^2}}}
{{{r=sqrt(900/pi)}}}
So the equation will look like 
{{{x^2+y^2=900/pi}}}
Since the general form is 
{{{x^2+y^2=r^2}}} where r is the radius.
Since they want it in exact values, this means that you don't divide by {{{pi}}} since you'll be left with decimal.