If x, y are real, show that  is valid only whenÂ
We know that  Â
Now, Â Â Â Â Â Â Â Â
and        Â
       Â
The equation  is possible only ifÂ
or if                             (Provided , )
or if      Â
or if           Â
or if                               [∵  is not <0]
or if            x - y = 0
or if                x = y
Hence, the equation  is possible when x = y