Question 867565
{{{x^2+y^2=18}}}, which is really {{{(x-0)^2+(y-0)^2=(sqrt(18))^2}}} is in the form {{{(x-h)^2+(y-k)^2=r^2}}} which is a circle with center (h,k) = (0,0) and radius {{{r^2=18}}} ---> {{{r = sqrt(18)}}}



Now simplify {{{r = sqrt(18)}}}



{{{r = sqrt(18)}}}



{{{r = sqrt(9*2)}}}



{{{r = sqrt(9)*sqrt(2)}}}



{{{r = 3*sqrt(2)}}}



So the answer, as simplified as possible, is {{{r = 3*sqrt(2)}}}. This is because this is simply a circle with radius {{{3*sqrt(2)}}} and when you have something like {{{r = 2}}}, you mean "a circle with center (0,0) with radius 2"