解原式={2/3X-2/(X+Y)[ (X+Y)/3X -(X+Y) ]}/(X-Y)*X
={2/3X-2/(X+Y)*(X+Y)/3X+2/(X+Y)*(X+Y)}*X/(X+Y)
=[2/3X-2/3X+2X]*X/(X+Y)
=2X²/(X+Y)
解原式={2/3X-2/(X+Y)[ (X+Y)/3X -(X+Y) ]}/(X-Y)*X
={2/3X-2/(X+Y)*(X+Y)/3X+2/(X+Y)*(X+Y)}*X/(X+Y)
=[2/3X-2/3X+2X]*X/(X+Y)
=2X²/(X+Y)