Suppose $we$ have this differential equation $8\sqrt[\phantom{2}]{x}(\sqrt[\phantom{2}]{9+\sqrt[\phantom{2}]{x}})dy=(\sqrt[\phantom{2}]{4+\sqrt[\phantom{2}]{9+\sqrt[\phantom{2}]{x}}}{)}^{-1}dx$

for $x>0.Ify(0)=\sqrt[\phantom{2}]{7},$ find the value $ofy(256).$