Topic: irrational function

the original function is SQRT((x^2-2x)/(x^2-1)) i tried to write this function in this way (SQRT(x^2-2x))/(SQRT(x^2-1)) but is not the same. When i look to the graphic the function lost some information....and the graphic is not the same. Can you help me to understand if is correct writing the formula  in this way or i made a big mistake about radical property?

Re: irrational function

Per default Graph does not use complex numbers when plotting graphs. The difference you see happens when you take the square root to a negative number, which will result in an error. If you enable Calculate with complex numbers in the Edit|Axes dialog, the two functions will look the same.