Question 362560
Leave the sqrt part alone firstly; 

{{{ 16*sqrt(x) = x-512 }}} Take square of both sides so you'll get;

{{{ 256x = x^2 -1024x + 262144 }}}

{{{ 0 = x^2 -1280x + 262144 }}} 

*[invoke quadratic "x", 1, -1280, 262144 ]