Question 34447
assuming you mean {{{ (x-y)/(x^2-y^2) + (x+y)/(x^2-y^2) - (2x)/(y^2-x^2) }}}, then


{{{ (x-y)/(x^2-y^2) + (x+y)/(x^2-y^2) - (2x)/(y^2-x^2) }}}
{{{ (x-y)/(x^2-y^2) + (x+y)/(x^2-y^2) + (2x)/(-y^2+x^2) }}}
{{{ (x-y)/(x^2-y^2) + (x+y)/(x^2-y^2) + (2x)/(x^2-y^2) }}}


so all the denominators are the same, so...
{{{ (x-y + x+y + 2x)/(x^2-y^2) }}}
{{{ (4x)/(x^2-y^2) }}}


so this is an answer. we can also factorise the denominator too:
{{{ (4x)/((x+y)(x-y)) }}}


jon.