For this case we have to by definition:
[tex]\frac {d} {dx} (x ^ n) = nx ^ {n-1}[/tex]
So, if we have the following expression:
[tex]f (x) = \frac {3} {x}\\f (x) = 3x^{-1}[/tex]
Deriving:
[tex]\frac {df (x)} {dx} = - 1 (3) x ^ {-1-1} = - 3x ^ {-2} = - \frac {3} {x ^ 2}[/tex]
Evaluating at[tex]x = 1[/tex]:
[tex]- \frac {3} {1 ^ 2} = - \frac {3} {1} = - 3[/tex]
Answer:
-3
