If x/y + y/x = -1, then find x^3 - y^3.
x/y + y/x = -1 ---> xy( x/y + y/x ) = xy( -1 )
---> x2 + y2 = -xy
---> x2 + xy + y2 = 0
Since, when factored: x3 - y3 = (x - y)(x2 + xy + y2) and x2 + xy + y2 = 0
---> x3 - y3 = (x - y)( 0 ) = 0
