(x-y/x+2y)/(x^2-y^2/x^2+4xy+4y^2),其中x=1-根号2 y=根号2-2

问题描述:

(x-y/x+2y)/(x^2-y^2/x^2+4xy+4y^2),其中x=1-根号2 y=根号2-2

先对式子化简 对分母x^2-y^2/x^2+4xy+4y^2=(x+2y)^2-y^2/x^2=(x+2y-y/x)(x+2y+y/x)
原式=(x-y/x+2y)/(x+2y-y/x)(x+2y+y/x)=1/(x+2y+y/x),再待数字计算