Add and simplify 1/(x-1) - 3/(1-x) + 2

im not sure if the answer is 2(1+x) / (x-1) or if it's 2(x-2) / (x-1)

please explain why

Apinhole camera is made out of a light-tight box with a piece of film attached to one side and pinhole on the opposite side. the optimum diameter d(in millimeters) of the pinhole can be modeled by d=1.9[ (5.5 x 10^-4) l) ] ^1/2, where l is the length of the camera box (in millimeters). what is the optimum diameter for a pinhole camera if the camera box has a length of 10 centimeters