# 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.

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