The function f is defined as $\displaystyle f(t)=(4e^kt -1)/(4e^kt +1)$

Find lim f(t) when t tends to infinity and sketch the graph of f.

Thanks, im baffled by the K which is a positive constant.

I found an asymptote on y = 1, and 2 point of intersection.

I can't find any stationary point there as $\displaystyle when f'(t)=0 , 4e^kt + 1 = 0 but 4e^kt + 1 > 0 $ therefore no stationary point