Function Rules

fg\left( x \right) =f\left( g\left( x \right) \right) \\ \\ ff\left( x \right) =f\left( f\left( x \right) \right) ={ f }^{ 2 }\left( x \right) \\ \\ gf\left( x \right) =g\left( f\left( x \right) \right) \\ \\ gg\left( x \right) =g\left( g\left( x \right) \right) ={ g }^{ 2 }\left( x \right)

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