题目

X平方-4分之x平方-2x 除以 (x-2-x+2分之2x-4 其中x=2+根号2

提问时间：2020-08-07

答案

原式=[(x²-2x)/(x²-4)]÷[x-2-(2x-4)/(x+2)]
={x(x-2)/[(x+2)(x-2)]÷[(x-2)(x+2)/(x+2)-2(x-2)/(x+2)]
=[x/(x+2)]÷{[(x-2)(x+2)-2(x-2)]/(x+2)}
=[x/(x+2)]÷[(x-2)(x+2-2)/(x+2)]
=[x/(x+2)]÷[x(x-2)/(x+2)]
=[x/(x+2)]×{(x+2)/[x(x-2)]}
=1/(x-2)
=1/(2+√2-2)
=1/√2
=(√2)/2