Plot[{Abs[Floor[x]/Ceiling[x] - 1], (1/x)}, {x, 195, 200}, 
      PlotStyle -> {Red, Green}]

Plot[{Sqrt[x + 1] - Sqrt[x]}, {x, 1, 2000}, 
      PlotStyle -> {Red, Green}]

Plot[{Abs[Sqrt[x + 1] - Sqrt[x] - 0], (1/(Sqrt[x]))}, {x, 1, 200}, 
      PlotStyle -> {Red, Green}]