For a
fixed element $a$ is a group $G$, define $$f \_ a (x) = a ^ {−1} xa , x \in G$$

Show that $f \_ a $ is a Homomorphism.

I know that to show that a mapping $f:G \rightarrow G'$, Where $G$ and $G'$ are two groups with $\#$ and $\*$ as their binary compositions I have to show that $$f (a\#b) = f(a) \* f(b)$$ 
But I cannot understand how to do that here.