x^2+2xy+y^2/x^2-y^2除以x^2+xy/xy-y^2
=(x＋y)²／(x＋y)(x－y) ÷x(x＋y)／y(x－y)
=(x＋y)／(x－y) × y(x－y)／x(x＋y)
=y／x
再将X=1
Y=-2011代入
原式=y／x
=﹣2011