Question 140338
{{{sqrt(81-x^2)=3}}} Start with the given equation



{{{81-x^2=9}}} Square both sides



{{{-x^2=-72}}} Subtract 81 from both sides



{{{x^2=72}}} Divide both sides by -1



{{{x=0+-sqrt(72)}}} Take the square root of both sides



{{{x=6*sqrt(2)}}} or {{{x=-6*sqrt(2)}}} Simplify



{{{x=8.48528}}} or {{{x=-8.48528}}}  Approximate by using a calculator



So the approximate value of x is {{{x=8.48528}}} or {{{x=-8.48528}}}