Answer
$s'=\frac{-1}{2t^{1/2}(t^{1/2}-1)^2}$
Work Step by Step
Take the derivative of the equation using Quotient Rule. Then apply Chain Rule to the inner terms:
$s'=\frac{(t^{1/2}-1)(0)-(1)(\frac{1}{2}t^{-1/2}-0)}{(t^{1/2}-1)^2}$
$=\frac{-\frac{1}{2}t^{-1/2}}{(t^{1/2}-1)^2}$
$=\frac{-1}{2t^{1/2}(t^{1/2}-1)^2}$
