Answer
$y-1 = -1/8*(x-3)$
Work Step by Step
The derivative of the function should give us the slope.
$$f'(x) = -(x^2-5)^{-3/2}, f'(3) = -4^{-1.5} = -1/8$$
We also find a point it goes through by plugging in $a=3 $to f(x) instead of f'(x)
$$f(3) = 1$$
In point slope form,
$y-1 = -1/8*(x-3)$
