Divide both sides by $2$.

$(\textit{x}-17)^{2}= \frac{ \textit{y} }{2 }$

Now find the square root of both sides.

$\textit{x}-17=\pm \sqrt{ \frac{ \textit{y} }{2 } }$

Now finish solving.

$\textit{x}=\pm \sqrt{ \frac{ \textit{y} }{2 } } +17$

Raise both sides of the equation to the $3^{rd}$ power, then subtract to isolate $x$. It is not necessary to expand $(x+3)^3$.