# Math Help - Derivative

1. ## Derivative

If
determine .

it gives me (pi5)(7t^6) but i dont think its the right answer

2. Originally Posted by wannous
If
determine .
$f(t) = \sqrt{5} \cdot t^{-7}$

$f'(t) = -7\sqrt{5} \cdot t^{-8} = -\frac{7\sqrt{5}}{t^8}$

3. aww thank i forgot it becomes negative