Question 265650
<font face="Garamond" size="+2">


The graph of a function crosses the *[tex \Large x]-axis at places where the value of the function is zero.  So set the function equal to zero and solve:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ f(x)\ =\ \sqrt{x^2\,+\,81}\ -\ 15]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ \sqrt{x^2\,+\,81}\ -\ 15\ =\ 0]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ \sqrt{x^2\,+\,81}\ =\ 15]


Square both sides:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ x^2\ +\ 81\ =\ 225]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ x^2\ =\ 164]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ x\ =\ \pm2\sqrt{41}]


John
*[tex \LARGE e^{i\pi} + 1 = 0]
</font>