# Functions and Vertex

**Algebra**Level pending

\(fg(x)=x-9,\quad g(x)=\sqrt { \frac { x+2 }{ 2 } } \)

If I use \(f(x)\) to make a graph, the vertex (or the turning point) of \(f(x)\) is \((x,y)\).

Find the value of \(x-y\).

PS: This is my first time to make a problem. If there's something wrong, please tell me.