Respuestas

2012-05-24T09:36:02+02:00

  x     x
--- +  ---
x+y   x-y

 

x(x-y)+x(x+y)
-------------
  (x+y)(x-y)

 

x^2-xy+x^2+xy
-------------
(x+y)(x-y)

 

2x^2
---------
(x+y)(x-y)

2x^2
----------
x^2-y^2