Answer
$f'(0)=2$
Work Step by Step
To find the slope of a function at any given point, all one has to do would be to look for the value of the derivative function at the same x value.
Given that $f(x)=\frac{x-1}{x+1}$, then the derivative function by the quotient rule will be $f′(x)=\frac{(-1)(x-1)}{(x+1)^2}+\frac{1}{x+1}=\frac{2}{(x+1)^2}$
As such, the slope at the point $x=0$ would be $f′(0)=\frac{0+2}{(0+1)^2}=2$