若将分式x^2-y^2/x+y中的y都扩大到原来的2倍,那么分式的值我的2x^2-2y^2/2x+2y后面怎么做，

Question

若将分式x^2-y^2/x+y中的y都扩大到原来的2倍,那么分式的值
我的2x^2-2y^2/2x+2y后面怎么做，

Answer 1

x^2-4y^2/x+2y
=(x+2y)(x-2y)/(x+2y)
=x-2y
,
2x^2-2y^2/2x+2y
=2(x^2-y^2)/2(x+y)
=(x^2-y^2)/(x+y)
=(x+y)(x-y)/(x+y)
=x-y