Answer
$ fâ\left( 1\right) =\left( 1+1\right) ^{-2}=\dfrac {1}{4}$
Work Step by Step
$f\left( x\right) =\dfrac {x}{x+1}=\dfrac {x+1-1}{x+1}=1-\dfrac {1}{x+1}=1-\left( x+1\right) ^{-1}\Rightarrow f'\left( x\right) =0-\left( -1\right) \times \left( x+1\right) ^{-1-1}=\left( x+1\right) ^{-2}\Rightarrow$
$ fâ\left( 1\right) =\left( 1+1\right) ^{-2}=\dfrac {1}{4}$
